Well, pretty much any answer would be better than that.
why wouldn't Jesus reminding them of the Law be the best answer, considering that they were trying to trap him with a perverted form of the Law?
The mob were convicted by their own conscience to leave until there was no one left besides Jesus and the woman, this verse wouldn't have done that.
of course it would, it would have reminded them that they were perverting the very Law they were trying to trap Him with
and they were all about the Law
It's all conjecture but a more logical answer would be Jesus writing stuff on the ground that everyone would have been guilty of, lying, hypocrisy etc.
or, with just a single reference to scripture, perversion of the Law
Your conjecture is just flat out absurd.
it really isn't artie, if you consider the crowd, what they were trying to do to Jesus, and what they were immersed in, culturally, since birth
they were slaves to the Law, and in one quick scribble in the dirt, Jesus showed them that they were perverting that very Law