Similar announcement re the lavs was made right before boarding my PHL-LAX flight a few months ago, and everyone sort of freaked out (myself included) and ran to the bathrooms.... only to find out upon boarding that what the gate agents should have said was that the lavs would not work UNTIL after takeoff and we had reached a certain cruising altitude.
I'm not sure what length of flight non-working lavs becomes a serious issue worth delaying a flight for but PHL to LAX is definitely past that length so I'm glad it turned out to be a misstatement.