Letting A Wash Settle ... but why?

[EternalAmateur]

Back with another question for those in the know!

I read somewhere that it is recommended to let a wash rest for a few days+, in the cool, before running it. My question is .. is this correct and why?

1) If the resting helps in the completion of the fermenting somehow, then that's great, I'll carry on doing it.
2) If though it relates to the settling of heavier particulates that are not wanted in the distillation process, here I'm having issues as I can't find a siphon that works well to take out the clearer liquid.

As I say, if it's (1), great. Nice and easy, thank you. If it's (2), what do people use to siphon - ideally something more than sucking on a tube! ... or is there a third option?

Thank you in advance.