I was lucky enough to speak with one of the guys who ported Final Fantasy VIII to Windows (A crazy talented guy from Naples and one of the earliest members of the OG playstation emulation scene) and the porting team of several IREM arcade shootemups to the Game boy advance (incidentally they were also from south Italy) and both of them told me the same story:

The source code they were given for the job was so specific to the assembler, compiler, build stack and internal company libraries and SDKs (which often they had no access to) that reverse engineering the final game was usually the quickest route.

> Certainly from the game historian's perspective.

That's a completely different topic, and I mean, sure - from an historical perspective it's absolutely essential, even simple changelogs become of enormous importance.