Let me know if I am misunderstanding what you said, because it comes across as salty to me.
If they signed the FOL then they already had the intent to leave for that facility; it doesn't seem like it is a ploy to get a different facility from the first because then they would be gambling on not getting a different one and being "stuck" with the first one.
If they accept somewhere they want to be but then their dream facility comes calling/is available, what difference does it make to anyone else if they jump ship to the other offer? I had 2 "dream" cities followed by 2 "almost dream" cities I put in paperwork for in the same month. I was selected for my #3 preference place (#1 of the "almost dream"). If #1 or #2 came calling I would absolutely have jumped ship to them because that is what's best for me and doesn't impact anyone else. Outside of "letting down" the other facility, where is the harm?