Because you are allowing company B to technically enter your home. But for them to do that wouldn’t Company A need a warrant for using Company B to enter your home? The same way as far as I know get a warrant to search pedo’s devices and entering home. I definitely know they need to have a warrant to tap your phone and stuff.
I don’t see anyone entering your home in this scenario.
If you broadcast your IP address in a torrent swarm, that’s now public information. Your ISP can match that IP and timestamp to a customer. None of this information resides in your home and there’s no wiretapping or anything like that.