Oh, sure, I'm making it all up. I just spent two months picking apart the Bosch e-bike system, I think by now I know what I'm talking about but feel free to prove me wrong and show me how you're able to get your battery to talk to a Bosch controller without using a Bosch BMS.
Hint: you won't be able to, the key is embedded in an NXP processor that has it's fuses blown (both sides, controller and battery) and any kind of hacking you want to do will have to be at the sensor level and even there I would advise you to use an older version of the firmware because the newer ones are very good at detecting such hacks.