To be fair most people (myself included) are so jaded by the constant misinformation or lack of care provided by airline front line staff that it's not a big leap for someone to think this was a lie, to get people ot stay in their seats. I mean there used to be a handful of crew that would say they saw "interference" in their flight systems from phones not on airplane mode, lol.
Had the pilot or FA spent 10 seconds communicating the technical reason passengers would've probably appreciated it, and learned something new. And I'm sure no one would prefer to take a delay vs use the toilet between 10-18k feet.