I’m sure you are correct about the differernces you have found. But I disagree with you saying “correctly” and “accurately”, as if every tiniest detail is supposed to match exactly. I don’t think Classic intended to recreate every tiniest detail of Vanilla, so that it was absolutely identical.
I am not sure that is even possible. But (as a software dev) I am sure that doing this would be a TON of work. It is much more work than Blizzard promised to do, when Blizzard agreed to create Classic. Instead Classic is “pretty close”. At least 99.95% of the game matches. You are right that 0.05% is different.
Blizzard only promised to add Classic because they could do that with a relatively small amount of work – much smaller than creating a new expansion – so they could handle 2 projects at once.
If Blizzard had attempted to reproduce precisely every possible detail of Vanilla, that project would have taken much longer and many more devs. We would be expecting Classic to launch in October (not 1 year ago), and Shadowlands would be “some time in 2021”.