That's not necessarily what's happening. Another plausible explanation is that when you deactivate your account, you're removed from various lists in the profil

That's not necessarily what's happening. Another plausible explanation is that when you deactivate your account, you're removed from various lists in the profile data of all your friends. When you activate it again, you aren't put back on the list until a regularly scheduled task runs (or until data propogates through the servers?). So if one of the lists is "deny from seeing these photos", you get to see them until that happens.