Earlier quoted context omitted.
It might be better if you didn't over hire. I can't speak for MSFT. But a lot of tech companies definitely hired to banana town. Cutting would be better than freezing salaries.
Hiring gives someone experience they sought and presumably would not have had (else they might have kept put). So overhiring in some light does look bad, on the other hand it gives some people the necessary experience for their next step in their carrers.
Not if they were let go before their first year, which has been the case at a lot of tech companies recently.
New hires, juniors especially, need a lot of time to onboard. Lessons in the first weeks and months of a new job will be more about company-specific tooling and minutiae, not engineering in the broader scope. Portable lessons come later, usually after you've found your legs.