Shimano also patents changes with battery... Sram can patent "its" battery, "its" clamping and similar things, but I don't see why other brands can't use removable batteries... Shimano has its satellite buttons ( patented ones are supposed) did not Sram take out his Blips?
There are strange patents like a 24mm axle between two bearings belongs to Shimano.
So came BB30 & Co, GXP, DUB,... giving us all kind of compatibility troubles.
For the wireless, it isn't clear. Plenty of legend like mine on forums.
https://bikerumor.com/sram-electronic-drivetrain-patents-show-wireless-road-mountain-bike-designs/ has a good overview but nothing on batteries.
It is strange Shimano and others are coming with semi-wireless, while they could do the same as SRAM.
Easier to setup and maintain, cheap batteries, that you can swap between components in case your derailleur is flat.
I don't see an advantage, except a longer battery life maybe, of a wired battery in the frame.