@RichardC10
... why plan to withdraw the locks above some (low) speed limit?
Maybe because of the following procedure drivers/considerations.
Imagine locks are discovered blocked or the locks operation system is discovered unserviceble. If this is discovered earlier in the burn, an engine shut-off, venting of remaining oxidiser to reduce weight and a reduced energy unfeathered re-entry may be feasible. You would not enter this abort mode unless you knew of the problem.
Imagine locks removed at e.g. Mach 1.4. Now imagine feathering pneumatics are discovered unserviceble much later, after nominal flight profile engine burn-out (2 minutes or so). Same problem! Or perhaps not quite? There may be redundant procedures for e.g. passive feathering (use RCS for correct attitude, then let it fold up "by itself" and keep it so using the trimmable elevators(?)
Fine, but you must unfeather again before hitting good old earth. Perhaps there are "tricks" for that as well. Or else bail out at lower speed and altitude?
In any case, with stuck locks that you´re not aware of, when you wait until full motor burn-out (for the nominal flight regime up to 380kft) there may be no alternatives left. I believe that may be a major driver for a not-too-late unlock action.
Admittedly speculative, but that´s what came up.
@Flash & peekay
I believe I did half rho v-squared on the numbers in SI units,
but will look it over, maybe a blind spot there ...