I personally think the whole 'lavs in your ticketed cabin' thing depends, quite frankly, on how scared the flight crews are of their passengers. Sometimes you get the announcement, which may or may not include the 'TSA directive/policy' nonsense (which IS completely made up, as others have attested to multiple times on this forum), sometimes you don't get anything about the bathrooms at all & you certainly don't hear anything about it on other carriers nor do they issue prohibitions on 'standing in the aisles, gathering in groups' etc. It's purely a flight crew specific paranoia, again in my personal opinion.