I think that's just visually giving you an idea of what's happening. Like I said earlier, I'm giving a simple naive presentation of how the system might work. Or, at the least, how I would design it without dealing with finicky shelf sensors. Ask anyone that has ever worked in a hotel with in-room minibars how well those things pan out in real life.
Unless that store is just a mockup and not how it really looks and works, I see nothing on those shelves or in the sky above it that is watching you put that cupcake back on the shelf.
The real way to find out is if someone in the demo video can pull their phone out of their pocket mid-trip and see their current inventory and total price. But I didn't see that in the video.
The girl in the video at 1:26 looks at her list and total, but after she's been through the exit turnstyle.
The video makes it look like it's constantly up to date, but that sounds quite complicated (despite dropping the ML, DL buzz words).
A friend at Amazon said he tried to trick it by taking two items at a time and it got it right every time, so yeah it does appear to track when you take the items.
But the video clearly shows the items being recognized as someone takes them from a shelf (and puts them back). The items don't need to be recognized at the time you walk out, the store just needs to know that you've walked out.