That HAD been the long-running excuse, not to mention a bone of contention w/AA for many in this Forum, which is why this 'customer service' thing was so startling. I know when I did the customer service interview w/AA last month I made a point of discussing this on-going habit of the flight crews to 'cry wolf' when it came to alleged security regulations that seemed to be made up on the fly.

Personally find it very odd ( incredible might be a more appropriate word) that
the lav would would be blocked for anything approaching 20 mins.
Usually the process goes fairly quickly .. but then I havent got the inclination
to try and time it

Well, on the flight I was on yesterday it was blocked & one or the other was out for most of 'How I Met Your Mother', which runs approximately 22 minutes w/o commercials. Not to mention several people in the cabin, including my seatmate & the girl in 1A (twice), tried to get up & use the lav while this was going on.