> half a millisecond is reduced.

I would like to caution against any significant changes to save microscopic amounts of time.  Twisting the code into knots for minor time savings is rarely worth it and it not what Python is all about.

> Half milliseconds is small, but it isn't negligible on some situation.

I would say that it is almost always negligible and reflects a need for a better sense of proportion and perspective.

Also, in the past we've found that efforts to speed start-up time were measurable only in trivial cases.  Tools like mercurial end-up importing and using a substantial chunk of the standard library anyway, so those tools got zero benefit from the contortions we did to move _collections_abc.py from underneath the collections module.

In the case of functools, if the was a real need (and I don't believe there is), I would be willing to accept INADA's original patch replacing the namedtuple call with its source.

That said, I don't think half millisecond is worth the increase in code volume and the double maintenance problem keeping it in-sync with any future changes to namedtuple.   In my opinion, accumulating technical debt in this fashion is a poor software design practice.