iCloud is always available as an option for hotspot regardless of whether your hotspot is currently active.
From Settings > Personal Hotspot:
Other debices signed in to your iCloud account will be able to use personal hotspot without turning it on manually.
This works even if your Mac is not connected to WiFi because Apple devices can detect each other using various methods, including Bluetooth.
When you’re done with the hotspot, just use the WiFi menu in your Mac to disconnect, or close your lid and stop using the Mac. The hotspot will automatically deactivate on its own.
This is a feature, not a bug, unless you’re talking about something else.
I don’t see any USB or Bluetooth only options on my phone.