Looks like I can stay in sunny Perth - 10.12.2 removes the stupid abbreviation dots!
Still no sign of any kind of preference. Bizarre!
Thought I’d throw in my 2 cents worth, because I’m trying it right now and it’s working. I use the yymmdd format because I’ll be dead before the next century hits (and I’m sure this technology will be as out of date as 78rpm records).
That said, I insert it into a file name by using TextExpander. I have a code for it, and if I use Insert Text by Typing all I need to do is leave a space after the code and it actions for me.
If that is working for you, then that's great.
However, you should be aware that a lot of software will recognize dates in the format of "YYYY-MM-DD", whereas they may not just using "YYMMDD".
For me the few extra characters is well worth the benefits.