As so often
"The transition from Xamarin Forms to MAUI should be smooth, but will nevertheless be a migration and not just a recompile of the source"
MS love changing things & then not providing tools to auto convert old code to the new variant. Lots of companies cannot prioritise the time and cost to migrate as it needs code changes not just rebuild, so technical debt accrues.
This is one reason windows mobile failed - lack of apps, as massive breaking changes across different versions of windows mobile such that anything 6.x or earlier needed essentially a full rewrite to work in newer versions of windows mobile, so in many cases it never happened (coders moved to a different platform e.g. Android)
That's why so much stuff for windows still gets written in winforms / win 32 APIs - because MS (so far...) dare not break those and so you are not playing with an ever moving target working on those "legacy" platforms.