We might say that humans as individuals do recursive self-modification when they practice at a skilled task such as playing football or riding a bike.

Those are first-order self-modification, not recursive. Learning better ways to modify yourself, or better things to modify yourself towards doing, would be second-order self-modification. ISTM that it would be very difficult to do anything more than a third-order self-modification on our current wetware.

Although our current platform for self-modification is extremely flexible, and almost anything stored in it can be changed/deleted, we can't make modifications to the platform itself.... which is where the "recursive" bit would really come into play.

(That having been said, most people have barely scratched the surface of their options for 2nd and 3rd order self-modification, recursive modification be damned.)