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…
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.
Can the same version of Word now produce the same rendering on two PCs? In the past (I didn't really check recently, I'm thinking more about 10 years ago) the same file might have had page breaks in different positions and things like that. I never understood if it came from slightly different versions of the fonts, from some info derived from the default printing or anything else...