The kind of meters we used to install 50 years ago would turn backwards if electricity flowed backwards.

So if you spent a week with the meter connected normally, then you swapped the input and output cables around for a week, the meter would be back at zero. Free electricity!

They used anti-tamper seals to make it more detectable, but there are ways around that sort of thing.

Maybe it looks like you're trying to trick the meter into running backwards?

I assume the scam would be you rewire the breaker so the grid is on the apparent load side. It's not exactly hard to do, just dangerous.