This is not quite right. At least in Debian, only files that are newer than some standardised date are to that standardised date. This "clamping" preserves any metadata in older files.
Strangely enough, sometimes using the epoch can expose bugs in libraries (etc.) when running or building in a timezone west of Greenwich due to the negative time offset taking time "below" zero.
Debian's approach is actually to use the date specified in the top entry in the debian/changelog file. That's more transparent and resilient than any mtime.
One of the authors of strip nondeterminism is here. The primary reason it's written in Perl is that given that strip-nondeterminism is used when building 99.9% of all Debian packages, using any other language would have essentially made that language's runtime a dependency for all building Debian packages. (Perl is already required by the build process, whilst Python is not.)
Any packages with "Essential: yes" (run 'apt list ~E' to see them) are required on any Debian system. Additionally, the 'build-essential' pulls in other packages that must be present to build Debian packages via its dependencies: https://packages.debian.org/sid/build-essential
Very true, but when there's literally 100s of years of women's legitimate medical complaints being dismissed (sometimes with fatal consequences), it is surely not too much of leap to speculate that this is part of the reason.