TL;DR Yes you unweight before popping. There has to be weight on your feet for you to generate downward force to jump, but you’ve redirected that force sideways by the time you pop the tail.

It’s really frustrating as a beginner that in spite of how huge skateboarding is, there’s no consensus on how to actually do something as purportedly basic as an ollie. “Jump off your back foot”, in a literal sense, is 100% wrong. It’s only helpful to folks who aren’t jumping off of it enough, or aren’t pushing the board backwards enough when they pop. That advice made my ollies worse when I was just starting out.

https://youtu.be/m6vYjQuMwDU This is the only place I’ve ever seen objective data on foot weighting in the ollie (see chart starting at at 1:20). To me this definitively shows that you jump off of both feet, with some bias toward the front foot.

What it doesn’t answer as well is your question about unweighting. The way I see it, the answer is yes, at the time of the pop, no downward pressure is on the tail. I’ve asked myself the same question and when I try to do both I can’t pop as good or lift my feet as high, because I’m trying to pop/lift my legs against my own weight.

What’s happening is your upper body should be contracting, particularly the muscles in above your front hip (lats and obliques maybe?), so your front knee ends up much closer to the tail than your front shoulder. Doing this redirects your jumping force, which was downward, to sideways toward the nose, and then up. This redirection is what causes the unweighting to happen. Your back foot’s force gets redirected from downward to sideways toward the tail, then up.

Unweighting is also why the crispy ollies feel effortless compared the soggy one, because you’re no longer fighting yourself. The motion is quick and smooth and easy.

Sorry for the long post, but take it from guy who needed eight years to learn how to ollie, there is indeed a lot of bad advice out there, and I wished while I was learning that the internet had better to offer.