No offense to Keystone, but from what we've seen from other manufacturers, it seems industry standard that the 'Bitcoin-only option' is the same hardware with a Bitcoin-only firmware.
Older keystone devices had the option of choosing Bitcoin only firmware, but you could not return back and install multi-coin version again.
Trezor also has bitcoin only firmware but I think you can always flash it and install multi-coin firmware on same devices.
The idea is to prevent someone flashing the 'regular' firmware with bigger attack surface, even if just temporarily, and getting their valuable Bitcoin seed phrase stolen. I know that BitBox02 Bitcoin-only works like that.
Not sure how bitbox firmware installation works but I know they have two different device versions.
As for Keystone, if I understood correctly they plan to release totally different device for Bitcoin halving, so both hardware and software will be different.
Let's wait and see... Bitcoin halving is in less than 90 days, so time is ticking away for Keystone.