It's nothing other than low-IQ sabotage, and seems so idiotic that it looks to be manufactured. I saw this on another site and had to point out how stupid it was.
What you're missing is the ability of the sheep to be afraid of something that they don't understand - i.e. the flap is the switch that tells the pump you want gasoline. As you pointed out, if it can't move, you can't initiate a transaction at all so the point is moot.
This "alert" went from social media to police and government warnings to news media reporting it as fact in about 10 days. Reminds me of the early covid days. No one checked or verified anything. It just was, and it sold a lot of newspapers so it was good business.
It's junque science, one of those "it could happen, almost" things. Close enough to reality that a majority will believe it.
Why fact check when you can have sensationalism.
They're a journalism, after all.