There's only two reasons I can think of why they'd patch the binary directly: either they've lost the source-code, or they no longer have an environment they can build it in.
If you can't rebuild it, you have to manually edit it, and when you do that you can't really change the addresses, not without a lot of headache.
I routinely update single page Powerpoints with more than 4 MB, due to the background image or logos.
The other thing to keep in mind is that Office documents are, in addition to being somewhat bloated internally, far more than just text. Think about all of the people writing things like documentation with hundreds of screenshots (all uncompressed BMPs), audio or video, etc. — and the people with those are far more likely to be at the kind of large corporations which expect value from their support contracts. There were multiple ways to deal with that problem but in general the easiest was switching to a 64-bit address space.
The point was that the code is too big and complicated, even for some of the best engineers in the world.
https://github.com/linker3000/Historic-code-PC-Pascal-and-AS...