This is all a matter of convention and misunderstanding. The lore of the game is artificially organic. It's not systematically laid out despite being systematically crafted; it is meant to bear the illusion of having gone through stages of real-world development. Take, for instance, the bestiary. The diverse biology of mobs in the game was systematically designed by lorecrafters, but our bestiary was clearly written from a
top down perspective that shows people were much more ignorant "when it was written" than we are "today." That's why the label "Coblyn" can apply to a genus, a species,
and a unique mob.
The term
Warrior of Light is "understood" differently by different NPCs at different times, but the label itself has a very specific, static meaning - and a lot of people are mistaking what that meaning is. In order to make everything clear, let's use some
temporary labels.
The First Wave
[Player Characters] of Version 1.0 who were awoken by Hydaelyn between the Years 1562 and 1572 of the Sixth Astral Era.
Meteor Survivors
Members of the First Wave who did not complete the campaign against Nael van Darnus. (Get Tattoos)
Twelvesblades
Members of the First Wave who interrupted the Meteor Project by destroying the Lunar Transmitter, leading to the Battle of Cartenau where they were sent into a rift by Louisoix. (Get Tattoos + Alternate Story Content)
The Second Wave
[Player Characters] of Version 2.0 who were awoken by Hydaelyn in Year 5 of the Seventh Umbral Era.
In the game's Lore, there
seem to be three possible reasons why NPCs don't recognize you.
- You are a member of the Second Wave, a new adventurer that has no reputation of note.
- You are a Meteor Survivor that did not build a noteworthy reputation in 1.0.
- You are a Twelvesblade that was cast into the rift by Louisoix tapping into the power of Althyk at the Battle of Cartenau.
Now that we've got all that out of the way, let's address this whole
Warriors of Light thing again. When NPCs try to remember the Twelvesblades, they cannot make out their features. They are a silhouette against the haze. For this reason, the NPCs have taken to calling them the Warriors of Light. Remember, if you didn't start the game with the alternative introduction, coming out of the rift, you were never sent into the rift. Either you were not at Cartenau at all, or you were weren't with Louisoix at the end. You are not a hazy memory.
One way to take this is that only the Twelvesblades are Warriors of Light, but
this is not the only way it can be taken. The only reason the Twelvesblades were able to achieve what they did is that they were chosen by Hydaelyn.
Every Twelvesblade was chosen by Hydaelyn, but not everyone chosen by Hydaelyn is a Twelvesblade.
Therefore, another reading would be that all of Hydaelyn's chosen are Warriors of Light, but that the Twelvesblades, who were the only Warriors of Light known to the NPCs so far, are the ones who inspired the term in the eyes of post-Calamity NPCs. This fits much better with the franchise narrative set by Final Fantasy I.
For evidence, let's look at two scenes of the game.
First, we'll examine a quote during the quest Lady of the Vortex. In this scene, Cid reflects on his amnesia. He can't even remember when he first donned the goggles that cover his "third eye." In order to ease his frustration, you use the power of the Echo to elicit the memories from his soul. As he watches them replay, he recalls more and more about his past. As the memory of donning the goggles returns to him through the power of the Echo, represented by a bright light, he sees through it to the source of this gift - the player - who symbolically hands the goggles (the memory) to him, thus breaking the wall in his mind and allowing him access to his full identity.

Originally Posted by
Cid
I remember everything... My name, my people, and my purpose. Everything. Come! It would be rude to keep Garuda waiting! It took a while for the memory to return, but I remember you. The floating isle, van Darnus... We ended it, that day─or so we thought. Listen─let's keep this between the two of us, for the time being. If word got out that one of the Warriors of Light had returned, the eyes of the world would soon be upon us─our enemies' included. And that's the kind of attention we could well do without. What, isn't it enough that I know the truth? Don't worry. A <man/woman> of your talents won't go unnoticed for long. Someday, they will remember you─and you'll never know another moment's peace!
If you are not a Twelvesblade, the scene ends after the black text. If you are a Twelvesblade, he refers to you by the NPC's convention of the Warriors of Light - one who was sent into the rift and, for most, beyond their ability to recall.
Next, let's look a quote from the final scene of
The Ultimate Weapon. You have just defeated the Ultima Weapon and are attempting to outrun the explosion while Gaius, who has sacrificed everything and failed, embraces the flames. Hydaelyn reaches out in response to prayers that the player be saved.

Originally Posted by
Hydaelyn
Warrior of Light. Beloved <son/daughter>. The Darkness hath fled before the unclosed brilliance of thy spirit. Yet it lingereth still beyond the sight of men, in forgotten corners of the world. In the depths of the abyss yet resideth the Dark One, watchful ever. Till this evil be cast out, never shall the world know aught but a passing peace. Yet for the present, a gentle light shineth o'er the realm of Eorzea. With thee at its heart. From sparkling mote shall it swell to glorious sun, and all the world shall bask in its warmth. Blessings and joy be upon thee. Go forth, my child, and be as a beacon of hope for Eorzea and the lands beyond, through all the days of thy life.