I think ignoring the board outline is a very fundamental error.
Is this changed behaviour as I never noticed the problem before?
A clumsy work round would be to create some dummy footprints with VERY long pads to place as walls at the edges of the board
This is related Routing around cuts ain't behaving
@cbernardo suggested adding keepouts. My tests show that this would trigger a DRC error, but would not contain the push and shove from placing the tracks in the first place