In this case, eBay is the shop, and I'm the customer. It's like walking into eBay and when I walk in I have to empty out all of my pockets and open my phone screen to show them that no one is telling me what to shop for (VNC).
No, because of the existence of client-side scripting with javascript, it's actually eBay that's running on your computer acting as the customer toward the shop that's your computer. You're right that the end effect is similar to having to empty out your pockets, but the underlying issue of why they're able to do that is a whole 'nother can of worms.
In this case, eBay is the shop, and I'm the customer. It's like walking into eBay and when I walk in I have to empty out all of my pockets and open my phone screen to show them that no one is telling me what to shop for (VNC).