I'm finding it hard to believe around 3 psi would have saved that tire (24.6psi min vs 21.75 - 23 psi what the team was running)... I'm no expert though and never played below 28psi on street tires.
You raise a very interesting point.
Perhaps the public info is not absolutely correct and the actual pressure setting was lower, keeping in mind we're also reading that there was a Michelin tire guy in their pit, and whatever the actual pressure was, was not a team only setting that Michelin was not aware of.
In addition, I have to wonder if there is some inflection point on the pressure setting curve, that results in a revised temperature rise curve and ultimate peak temperature.
The same thing might hold re the carcass flex, keeping in mind the carcass will have a "stiffness curve" as relates to displacement, frequency and temperature at the least.
Look at it this way, the tires are a ragged edge design servile to a host of parameters, some being mass, 4th moment of inertia, grip in various planes, and adequate stability (= acceptable instability). Reduced pressure increases carcass flex which in term increases temp as the flex energy gets transformed to heat energy. The chassis guy and the rider want more forward drive grip and sidewall deformation for lean grip, which a less stiff carcass provides, as can be realized by reduced pressure settings. Perhaps the range of problematic temperature rise and/or problematic/destructive carcass flexure starts at a low pressure point that would surprise us IF we were ever able to find out from Michelin. (same concept would hold re any of the racing tires regardless of the supplier)
By the way, Sheene's 1975 crash was in effect to unwitting and unintended destructive testing of the Dunlop slick rear of the day. Very painful way for Sheene to unintentionally provide Dunlop with a discovery of what they simply did not priorly know.