I expected something different too, but people saying the whole game is trash as a result is an overreaction.

Stormblood will probably be amazing, have an amazing story with lots of epic moments and a lot more dev time spent on it than this little bonus fight we got today.

I think they just could have told us more about this instead of making it sound like a secret worth keeping. If we knew it would be something much less than a regular trial, people wouldn't have been as disappointed.