Historically, time and os modules have been considered low level, thin wrappers over system libc functions.  Users of these modules are the proverbial "consenting adults" who should understand their power and the associated risks.

The place to provide a better behaved strftime function is the datetime module, but I would leave time.stftime pretty much the way it is and would only consider making *fewer* checks on Windows if _Py_BEGIN_SUPPRESS_IPH / _Py_END_SUPPRESS_IPH macros can indeed help to avoid crashes on illegal format strings.