If someone actually got "pixel-faithful" Office documents rendering correctly, MS would be screwed. That's actually really important for a lot of companies that carry around decades-old templates that never look exactly right in LibreOffice or any other software that attempted to replicate it.

The slightest misalignment of a paragraph means a line on page 27 of 120 now moved down by 2 pixels, screwing everything else out of alignment. Yes, plenty of companies pay Microsoft 365 subscriptions because of exactly this reason; it sounds ludicrous when you think they could just pay someone to replicate the formatting in a different suite a lot less than the subscription costs, but that's not how it works...

I've heard that the same file can render differently in MS Word across different machines and OSs. So, that won’t help either.

Sadly, Microsoft 365 is not “pixel perfect” compared to word. I often run into headaches where line numbers are different between the two and content ends up on different pages.

If Microsoft can’t get consistent rendering of word docs between Word for Windows, Word for macOS and Office 365, I don’t like anyone else’s chances.