Some of the more clever APs monitor the client signal strength and deauthorize the client when the AP decides it should switch to a different access point. The client should then attach to the best AP. Of course, the devil is in the details as the AP decision is "deauthorize a client when another access point can offer a substantially better connection" which means the AP had to know about the other AP points the client could use and the client signal strength at those access point. And, of course, "better connection" involves more than signal strength as AP load matters as does the band, as does the connection speed to the other device. For example, at some locations in my house, the fastest route to the Internet may be different than the fastest route to a local server.