If the physics simulation is correct then you shouldn't need a button to save any crashes that are actually savable?

It's definitely not an important issue, but technically MCF is correct. In GPB, if the virtual rider is involved, you are not completely in charge of the bike (DST is something else). MM is able to save a lot of situations where he is losing the front wheel, due to leaning his body even more to the inside, pushing his knee of the ground and steering to the inside of the corner (standing the bike up). He does all this with admirable reaction time and therefore often enough is able to save the bike from lowsiding. But he does not manage always, because you can only do this when the bike is still on the brink of losing the front and only if the tire can regain traction if lean-angle is reduced rather quickly. But within those Parameters, if a "save" button would do exactly what MM is doing, it might even make sense to have it and would actually be realistic the bike could be saved from time to time. Only gripe I see is that someone might be button mashing "just in case". So the virtual rider would really need to lean to the inside even more, steer to the inside and stand the bike up in a way that would make you run wide. So button mashing would let you run wide and would slow you down considerably. Then it would even make sense.
Speaking of all that. What I am missing in GPB is the real danger of risking low-siders when having lean-angles and/or braking into Corners. In real life most crashes happen this way. In GPB you almost never are in danger of losing the front due to hard cornering and/or braking. The front seems to be on rails most of the time. It used to be way better in previous betas (from what I remember it felt really good until beta4 or beta5). In those early betas one had to brake smoothly into corners and one had to reduce brake force on the front while leaning into corners. Riding a bike in GPB even made me a better rider in real life! In recent betas the front feels too much on rails and I have the feeling that the virtual rider limits the max leaning while braking, so effectively the player does not really run into danger of losing the front. It becomes even more obvious when running in the rain. It used to be one of the greatest feelings for me in the early versions of GPB - to slowly work towards that limit of the tires while braking hard into corners. After all, that is one of the real thrills of riding a bike competitively irl.
If Piboso reads this:
Please bring back the dangers of low-siding! It is a simulation after all. I don't need the virtual rider to take that thrill away from me. I might even consider riding in GPB again if this thrill comes back.