I've never actually had that moment with a beta reader; I've never really had an actual beta if I'm honest. A few times I've had friends read through a work (and some of the comments they leave on it as they read do feel the way you're describing, being in sync and someone just Getting It) but I've still yet to find someone with whom I click on a level that we can be like... working together on writing to that degree.

I'm really glad for you! That's definitely something to treasure.