Hiya! First off, thanks so much for sharing these schematics and symbols and part symbols, I've learned a lot for my own personal projects ever since buying some of your FeatherS2's!
Looking at the Power Path on the schematic for the OMGS3, it seems like there is supposed to be an USB power connection to the net attached to the gate of the battery isolation PMOS (T3)? Without it, I don't see how the gate would ever be closed if battery voltage is present.