I'm not sure exactly, but I know that it's possible to...
Assign a shimmier just in front of an incoming platformer, so that the lemming (as a Reacher) jumps, the platformer places the next brick while the Reacher is in the air, and the Reacher falls and lands on the platform.
However, this doesn't involve jumping *through* terrain - it involves timing things so that new terrain is created during that small window where the lemming is above the location of the new terrain.