Re: I don't get it
I would say it must be very cobbled together, but then that would be an insult to cobblers.
Kidding aside, I think it really hints at how applications that handle many document formats will have separate code bases for families of formats. Even more, the thing about macros, scripting, languages, and the such is that we can reasonably expect multiple interpreters--each with their own code bases.
Wait, does Office support anything other than VBA? Sorry, time for a bit of research. Yet, I'll leave the point above stand as a general concept.
Sure, I like to take a poke at Microsoft when I get the opportunity. But, those of us who don't use commercial software (except maybe some drivers) need to watch out for this as well. Surely, this is a key anti-pattern that we're looking at here, and it could well happen elsewhere and likely has.