3590.50 Should Serials Always Match?

I've read a lot of conflicting info regarding whether 3590.50 Speedmasters case serial should match the movement number. I've read people say with conviction that it should ALWAYS match and others claiming to be watchmakers who think they don't necessarily match until the late 90s. Most of these threads are a few years old. With the late 80s and early 90s tritium Speedmasters quickly becoming considered vintage and prices going up, I feel like the correct answer on this should be documented somewhere right?

This question is particularly acute for me because I'm considering the below watch and I think it may be a franken due to the mismatch. If not for the mismatch I'd think it a pretty decent early 90s 3590.50 with very pleasant tritium. What's the braintrust here think?

Why wouldn't they match, because the whole reason for putting it on the outside is that it matches the inside.

Thanks all. Makes sense to me that they should match or somehow be off by a very small number by rare human error during production. But Speedmasters are a strange animal with many peculiarities. Wanted to make sure where wasn't something I didn't know I didn't know, especially on these less meticulously documented 90s variants. A shame this is a franken, really like the patina