Dan,
If true probably a combination of not wishing to take undue safety / reputational risks near the end (careers could be effected.....). The temptation to push a little too hard on ‘fini flights’ knowing that an army of camera-toting spotters will be at the usual sites could be too much for some to resist. Seems a little draconian, and, subjectively, a sad way for a low-level penetrating bomber to finish.....