Ha nice. The physics with frozen things always do weird stuff on this and fusion, like when you spin against them you just like end up standing on top instead of pressing against the side and going up and over, or if you stand on them there's no knockback.
Yeah, I kinda wondered if this might have some TAS application. I doubt it's very useful, although I'd be delighted if someone proved me wrong.
I was also able to induce the glitch by rolling under a frozen rinka and unmorphing, although I only went a few pixels into the block. I think I recorded that too, so I'll see if I can upload another video.
Here are two more variations of the same glitch. In the first, I deliberately cause the glitch to work but only go a few pixels into the ground. The other video is really just the same as the original video I posted but it's more exciting since I fall through a platform.