There is The Navel normal, The Navel (Hard) for level 50, and then The Navel (Extreme). These all appear under the "Trials" tab in Duty Finder, which you can open with /dutyfinder. My guess is that you did The Navel normal instead?

It's important to note, however, that (Extreme) or Minstrel's Ballad are considered the actual hard versions (High-end duties). These will be unlocked via sidequests in the same way. They don't have a story quest for the higher level ones because it goaded new players into unlocking high-difficulty content by accident. If you queue for the Extreme version, it may take hours or days to get into, because it only matches you with other new players that queue for it or a small minority of players that have access to Mentor Roulette. It's not filled by the roulette everyone has access to, which is Trials roulette.

If you do get into the Extreme version, you will probably beat it because of gear and echo stacks, but it may take a lot of attempts. Just something to be aware of! The alternative way to clear Extreme or Minstrel's Ballads is to do it solo when you are higher level (for example, level 70 in level 70 gear) using the Unrestricted setting or if you have a level 100 friend that can help.

A lot of things like this are confusing at level 50 and lower, because that was the beginning of the game, where they threw mud at the wall to see what sticks. It's a bit like the pilot episode of show. They don't repeat all these design mistakes later on. After level 50, you'll only see the (Hard) versions as part of MSQ and won't even run into any other version at all unless you go out of your way to.