It is true if you pass in appropriate choices for f. The solution is to document appropriate choices directly. Right now it’s quite indirectly documented in sort!:
the lt keyword allows providing a custom “less than” function
So the footgun, aside from the indirect documentation, is that <= seems like a reasonable choice for a “less than” function to you. So a solution would be to add e.g.:
Note,
<=is not a “less than” function.