Electrically? Yes.
Mechanically the expansion card has higher durability because the force on the USBC is minimized. It's also convinient to have build in "carry slots", so for your standard loadout you don't need to bring a bag with accessories. Compare it to the dongle storage in a wireless mouse.
Batteries have one advantage over over supplies: extremely low noise. Even an good LDO will bump up the noise floor, and a cheap lcsc part will do so too. Plus you's want a reasonably low dropout and quiescent current, which also increases price. Maybe 10ct in volume is reasonable for such a part - and yes, that will absolutely eat the margin