> 99.9% of people using Microsoft Office are using it on one computer. I'd wager the majority of those people aren't using only Microsoft Office and nothing else.
If you step outside the tech bubble, yoı'll see Microsoft Office is actually used to do, you know, office work quite extensively. If you work in a big enough company, it is probably an Excel file transferred from your company to the bank that paid your salary. This is its major purpose and where it is being used predominantly. As you can guess, those files are being shared accross computers that run completely different OSes.
Word is a word processing program. Its job is provide a consistent experience in paper-form document generation. Its job is to be useful and consistent regardless of the underlying system. It gives you suggestions based on its own dictionary that has extra metadata. I doubt that your system has the exact metadata it has.
It could be a reasonable ask to support injecting words from the system user dictionary but those are rarely the formal words one would use regularly in Word.
