At some level, shouldn’t choices where one option is strictly better not surface as configurable choices at all?
If I have to memorize sets of behaviors by “compatibility version,” don’t I now have to remember lots of sets of particular footguns, across time and across systems that I work on (or parachute into)?
I read an essay about XML once where the author noted that he got a warm feeling inside whenever he saw the opening tag:
<?xml version="1.0">
He noted that there were no higher versions. (Though they're now up to 1.1.) But he considered that the inclusion of a version number from the beginning of the standard was a shining example of why they hadn't needed a new version.The premise of your question doesn't work. If one person is going to learn about the option and a second one isn't, the better system for that to occur in is the one in which more people end up with correct behavior.
In this case, that means surprising the guy with existing (buggy) software; he'll have to fix the bugs. It means not bothering the guy who's starting a greenfield project. Neither of them will be subject to this bug.
The alternative, which you seem to be saying you prefer, is that the guy with buggy software should continue to have bugs, and the greenfield guy should also have bugs.