I applaud you, sir Gigachad, on bearing the noble burden of carrying your shopping in a backpack. I've been there, and it's not very comfortable.
Great detail on your strategy, too. Though I think I'd rather avoid panicking for time to pack. It's either the leisurely self-checkouts for me, or if on the unavoidable occasion I have to directly interact with another human being, simply speedrunning IRL Tetris with the button-press sequence already etched into my mind.