In what way? Extends / shortens fly? Or just landing?
Only way to prove I guess would be tool-assisted replay.
It gives you like a little boost, makes your worm go a little bit further, it isn't a huge amount, but enough to get past a spike, about 1/2 or 1/3 distance of an average cup size if done at the right time.
It has more effect before it reaches it's "peak" point, which it when the worm stops climbing, and starts falling.
Once the worm has started falling it has no effect(from my experience).
Closing the drill at the exact time as your worm lands which makes u stick to the ground instead of rolling.
So yes, it does make a difference, even if slightly, it's still a valuable feature.
One way to prove it works, is by doing the Luigi Remix map, the one where it's almost impossible to reach 30.
9/10 you will reach it only by using this boost.