This one is completely on me, lol! With this room- it was meant to serve as a visual "depth trick" of sorts - the area you got to was not intended to be accessible, but there is a room NW from the "hub" where you can jump across platforms, and on the other side, you will reach a cliff with this key piece. ;) This was mean to be a "hint" of sorts.
On the next update, I'll reinforce the wall here and swap that key piece out with a "dummy" one.