And that thingy then is the direct outcome of it coiling itself up as at that point it is already fixed at both sides.

- Well at least for my sample size of 1 it was.

I observed that when my cucumber plant grew over to the pitcher plant.

This is caused because it first grows straight over and then wraps around the destination. And after that it does that helical thingy to get rid of extra length.

And that extra length exists because in order to find the destination where it wants to connect to it basically sweeps left and right while growing until it hits something to hold onto. But it may slide off multiple times until it is long enough.

'Tendril perversion perversion' describes a research phenomenon where you look up something on Wikipedia and one thing leads to the next and you spiral down a vortex of interesting information until suddenly the spiral turns and the vortex sucks you deeper and deeper into useless bullshit.
Its funnier than the interesting information, thats why it sucks harder.

Gardening tips with Urotsukidoji.

It's how the tendrils shorten themselves, to pull the plant towards what's supporting it.