Which they co-opted from protesters in the 60’s, rallying against the Vietnam war, which they co-opted from the Revolutionary war, where (allegedly, much harder to source), the revolutionaries also flew the Union Jack inverted. Its history to mean insurrection in the US is as old as the US.
Its been used in many other instances internationally, and yes, also at sea with a much deeper history to signal distress. Regardless, the pedantry is both technically and figuratively misplaced.
which they co-opted from the Revolutionary war, where (allegedly, much harder to source), the revolutionaries also flew the Union Jack inverted.
If they did, I assume a half dozen vexillology enthusiasts with good eyesight got very concerned.
also flew the Union Jack inverted
How could they tell?