Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay... "
That was disappointing for me. Specially condidering the Steam Frame's controllers make use of AA batteries: "One replaceable AA battery per controller, 40hr battery life"
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3' Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
Just to piggy back on what you are say, one of the engineers in the LTT video mentioned they want to team up with iFixIt again, just like they did for the Steam Deck. And I saw the back shell off the controller in one of the videos. The batter looks dead simple to replace. It's wild to even imagine that a company in 2025 would be be consumer friendly.