Aluminum gets softer fast as a function of temp.
The more air that is in the cylinder, the more pressure and transfer of heat.
Add the cylinder pressure for more force, and you have the ingredients for forming the aluminum. When we were running 30PSI and 2000 deg with 1100ftlb, the pressure and air density were not getting the aluminum hot enough, fast enough. 2000 deg at 45PSIA (30PSI boost) is not the same heat transfer as 2000 deg at 75PSIA (60PSI boost). It takes "mass" and temperature to exchange heat. Thinner air, less fuel, regardless of temp is not as dangerous.
So we know based on physics the piston itself will get hotter at the same HP with more boost at the same EGT, because there is more mass of "hot stuff" to heat it up.
Seems piston cracking on fuel only is still pretty rare regardless of HP at 40PSI. The rods might bend, but the pistons tend to be intact.