It even occurs with human checkers but it’s quite rare (barcodes are fixed now, or the stickers destroy themselves if you try to remove them like at Goodwill).
The attack apparently would have you swap a barcode but still on camera scan it which I guess theoretically makes it harder to prosecute but I kinda doubt it.
It also helps catch misscans which is probably much much more common (someone scans an item, they thought it scanned, they put it in bagging area).
If you don't scan it and you put/keep it in your backpack, that's not different from doing the same but going through the cashier checkout right? They already had that problem, so if they keep that as it was but reduce the amount of personnel, that's a net positive?