Coincidentally, I just used the hotspot mode last night, and can confirm that it does work (on my hardware, at least).
edit: but I am not connected to any other wifi network at same time
Was momentarily tripped up by network IP address being 192.168.43.* rather than the more usual 192.168.0.* or 192.168.1.*
Once laptop is connected by wifi to Android hotspot, I can ping the Android device (gateway = IP 192.168.43.1)
Give that a burl.
I am thinking that perhaps your home network has clamped down any non-standard port numbers, and perhaps that
B4A-Bridge on port 6789 has been caught by that.