Probably not.
Those are usually connected to a wheel lock. So when the device detects the fence it locks the one wheel it’s attached to. The whole device looks something like a plastic fender or cuff surrounding about half of one wheel. The sensor / antenna is built into the device. Grocery store cart wheel lock - Google Image Search.
If it was a separate flimsy wire, people would simply cut or break them off first then steal the cart which would no longer detect the fence since its antenna was absent.
IMO the folks claiming this is a static dissipater are correct. The tendency to build up static electricity depends on temperature, humidity, floor material, cart wheel material, and customer clothing & shoe material. The first 4 items are local to each store. As a result, some stores in some areas are prone to it, and others are not. I’ve never been static-shocked by anything here in Florida. It used to happen to me routinely in St. Louis, mostly in winter.
So it makes sense that some people have no idea this is an issue and have never seen these things while for other people it’s a bigger deal and dissipaters are becoming commonplace in their area.
FYI here’s a thread I started a few months ago asking questions on the topic of static shocks in the wild. I learned a few things from folks there and you might too:
In which one person mentions Wal*Mart shopping carts as their big source of static shocks. And in which another provides the remedy for impending shocks: