You aren’t crazy. I remember this being posited as a wifi alternative too. They claimed you could have a Bluetooth signal that wouldn’t reach beyond the walls of your home, preventing outside people (neighbors etc) from piggybacking on your network even if they had a password or the network was open because of the short range. And that tech does sort of exist today. A lot of mesh wifi routers use Bluetooth to connect to each other and provide that wifi to you in whatever part of your home you happen to be in. IOT devices do this as well. I believe this was called a piconet. But it never caught on, and I think it was more a theoretical idea than an actual real push.