Just spitballing, but a new part number means new variations to account for, new testing, new code, new hardware (balance/charge rate/cooling system), and new safety verification.

It’s cheaper to hire a lawyer and programmer to screw a customer than a team of engineers to appease government.

Reminds me of CD/DVD drives. Manufacturers build/test one model, and make 3 firmwares with software limits to market to low, middle, and high price users. All models make profit, but segmenting the market gets those who can pay a little more. The advanced users buy the cheapest drives and reflash them with the best firmware to restore function.