> There's no standards body for these things.
Yes there is -- it's called CUA (Common User Access)
"The subset of CUA implemented in Microsoft Windows or OSF/Motif is generally considered a de facto standard to be followed by any new Unix GUI environment."
The original Mac predates that, and I think it is quite conceivable that "Enter" to select a file name and edit it was in use back then.
Yes, I can confirm that it's been that way (almost) since the beginning.
Apparently[1] the original intent was to allow the user to just type and rename the file, but the enter key was quickly added after they noticed that the display models all had garbage filenames. It was an early tweak that stuck (much to the chagrin of those of us who also use other systems). Why they never added it to the context menu is beyond me.
[1] https://www.folklore.org/StoryView.py?project=Macintosh&stor...
When you say the 'usual' function keys... do you really mean some other system's function keys? Why would you expect macOS to use the same function keys as a different system? There's no standards body for these things.