There are temptations to cheating on limits: the pax are happy to get to destination, they book with you again and tell all their friends how good your airline is. The cowboy operator stays in business while the fly by the regs operator goes out of business
There are margins built into approaches. Likely one could determine a hyperbolic curve mapping deviation against increased risk. A 50' cheat might bring the risk up from the 1/1,000,000,000 beloved of regulators to 1/1,000,000. A 150' cheat might raise the risk to 1/1,000 or worse.
Note that the odds remain very much in favor of the cheaters -- as long as they don't hit anything. One of the better examples of skill beating out judgement was an accident at Sioux Lookout where the a/c hit the on airport NDB mast
In this case, it looks like there was a low level loss of control (stall, VMC?) which raises the question of who, if anybody, was minding the airspeed.