Yeah, not every gym has to unlock stuff. First gen did this because there were only 5 HMs. What HMs are we having in this game? There are 9 total in generations 1-3, so at least 3 gyms have to not unlock an HM. To name them:
Cut
Fly
Surf
Strength
Flash
Whirlpool
Waterfall
Dive
Rock Smash

Which ones are in Topaz?