You can not join a world from a device that you have hotspot to because you are "not connected to WIFI". Used to work in MCPE 0.7.0 ~ 0.12.0 (before UI change)

TO REPRODUCE
1. Host a hotspot connection (on phone)
2. Connect with another device (running compatible version)
3. Open a world to LAN on the other device
4. The phone will see the world but will not let you join, see attached.

It is possible to join the other way though because "there is WIFI connection" This is NOT exactly the same as MCPE-60162