Well the announcement regarding in lav use etc comes in various combinations
while you might be surprised to hear the "customer service" expression/reasoning used but its not even remotely "new"
Crews have used various reasons including such as " TSA directive", " FAA rules", " AA policy"

However in the scheme of things does it really matter? Not to me it dont.

Passengers never seem to be able to pay much attention.
Six F segments in the last week and without exception there were sometimes mutiple lav users coming from Y.
Incidentally all those were over 2 hours and only once did the FA do the lav blocking procedure.

mike