Spoiler Does it involve holding the draggable at a half-grid midpoint? That seems like the only way I could solve it but it isn't a trick I could replicate consistently
Is this the right way to solve it? Spoiler I used the autopilot technique, and B-bot managed to extend it's legs to slightly touch the win block. I agree with @cpw as well; the trick can't be repeatedly carried out.
Spoiler: Solution move the slider,click the stone block near the win,move fastly the slider and when he touches the stone block you tap immediatly to the win
In the scope of this little level, rattling with the draggable was an intuitive measure to take. In a larger level I would consider it cheating (not unlike the boogie bot bug trick). Furthermore, I ended up with B on the opposite side (back on the side where he spawned) more often than not.
I like the trick in the Illusion much more. It is more consistent. I, however, don't immediately see much use for it in a level design.