Why is "It's something to do" apparently a valid defense?

[Alahra]

One thing to note though is that the relic weapons in 2.0 have always bee nreferred to as "Zodiac weapons", but not even the ques tline itself ever refers to it until the animus stage (with the zodiac braves). That at the least has implications that they intended this to be a questline that would be added on down thee road past the zenith stage.

They weren't referred to as Zodiac weapons originally--the first mention of them as Zodiac weapons wasn't until 2.2, when they added the Atma/Animus stages. Up until 2.2, they were referred to as Relics (the quest title was A Relic Reborn).

And I did find one of the interviews I was thinking of, but it looks like I edited it in while you were writing your post. The gist is that Yoshi says they added the Zodiac weapon questline specifically to address player feedback desiring another way to acquire weapons. He doesn't say that they're changing their future plans regarding Zodiac weapons--he says that's why they added them in the first place.