I have yet to see a commercial aircraft flight manual which prohibits fight into cbs i.e. a restriction requiring avoidance ‘at all cost or else’.
Quite. Doubtless you've also not seen a commercial aircraft flight manual which specifically prohibits flight directly in to the face of a granite wall...yet somehow we all know it's a stupid thing to do.
Neither is the aircraft designed for that event, neither is it designed, nor intended, to be flown into a cumulonimbus cloud.
Part 25 makes you no gaurantees.