Oh god dammit of course it's something that obvious. I was getting confused since I couldn't figure out how to pass through blocks in general and I assumed the game just didn't let you do it and I assumed the blocks must be breakable from above, somehow. I also figured out the misleading side room is actually telling you how to use enemies for platforming.See these half blocks on the very right? You can pass through them by pressing down and down again. Took me a while as well.
Gotta say that the movement in this, particularly the jumping, is a huge exercise in frustration. The camera works mostly fine but it's really awful when you need to wall-jump up on a platform completely blind since you can't see your character anymore. Combine this with kind of awkward controls that feel rather unresponsive and it doesn't exactly make me confident the full game will be able to deliver on the gameplay front.