Those are being used wirelessly.
If you have them plugged in then they shouldn’t drain, and if they do it’s very slow. I have never run down a quest plugged in, pretty certain my q1 and q2 both charged while plugged in for Oculus link.
For wireless the 2 hours of each battery is fine and normal, but for native wired PCVR it’s a first. I think they should be able to fix it though, probably just a quirk of the prototypes.