I'm not being facetious, can you direct us to which laws are in play here? Specifically, why different models can be classified as different exports that need separate approvals?

Section 5 Part 2 (Information Security) of the EAR Commerce Control List likely applies.

IANAL; you need to be one to interpret this stuff. These laws are as thick as a dictionary.

The EAR dates back to the Export Administration Act of 1979 but it was mostly overhauled by Congress in 2018.