Gather a sufficient amount of people, and you will find someone willing to do anything. FL’s player base is large enough, and the requirements for a chess-match are low enough (read: almost nonexistent) that, if there’s a way to abuse it, it will be abused every now and then.
What I can’t help but wonder is why would that be “abuse”, since IIRC even if you lose a match you gain some rewards - and I don’t remember any accompanying menaces, qualities tracking losses, or other penalties. So the only reason to run from a match would be to spite your opponent. I honestly wonder whether that’s a real problem, or whether FBG are just over-engineering to fix things that don’t need fixing, to the detriment of everyone’s convenience.
The same mechanic is used for Sparring (lethal or not) and also for the election debates. And in those cases there were penalties for losing, so I understand their reason for blocking withdrawing at the last step. But it’s still a problem with these mechanics.