This took me a little bit to figure out. When you pick a seed, the door to test that seed closes. You have to try before you choose. So what happened is you chose Thwomp, but then tested Avalanche on the other side because you only saw one door.
Oh, goodness, I really don't think that's how it should work.
I think that seed selection in the seed rooms should only be set once you leave the room.
1. Enter a seed room
2. Pick a seed
3. Enter test room
4. Try out seed
5. Leave test room
6. Grab other seed, first seed grabbed returns to its pedestal.
7. Repeat until you leave. When you leave, that's the seed you picked, the other seed disappears if you return to the room.
That makes it all way more discoverable without having to explain how it works. If you enter the room and just try and grab both seeds, it's self evident you can't (because one seed returns when you grab the 2nd) and the "pick and seed and then test it out" is super intuitive.
That feels like adding an unnecessary step, though.
If you make it so that you can only pick one seed, and if you pick up the other, the first returns to its spot, you succeed in capturing all the functionality you want, but with one less layer of abstraction.
Especially since the videos of "how does this work" appear over top of the seed. Going near the need you want to test to see what it does, but not touching it, feels super unintuitive.