Tell that to the people who write L.append(1, 2, 3) despite that it was never documented. :-(
I do -- if and when I see that (haven't seen it in ages). Technical managers at development shops know about stuff "accidentally working" and are more tolerant of bug-fixes against that than of other backwards-compatibility breaks, in my experience.
Hm. This was widely complained about, probably because many examples (including in books) got it wrong.
fwiw, these days, I get
TypeError: append() takes exactly 1 argument (2 given)
far too often to think that I picked this up by reading the wrong books. it's an easy mistake, and it used to do the "right thing"...