Look up the target method. They can automatically connect your face/payment ID to items you haven’t scanned. They get you after you’ve racked up enough cumulative value that you haven’t paid for to count for a felony.
So no, they aren’t sticking you with a felony charge for a loaf of bread. They’re sticking you with a felony charge for enough loafs of bread to value a serious theft charge.
It’s not going to effect you if you only ever stole one loaf of bread. Waiting until you commit enough theft is the cutting corners part you’re talking about.