If it concerns you, don’t use your phone as a hotspot. Get a proper mobile router that gives you far more granular data and far more control. The mobile router can sit between your phone and all other devices. Grousing / being salty about Apple is not going to make your data and traffic issues / worries any less. Your data is your responsibility.
Don’t just “be concerned from a privacy and security perspective”. You are the one who chooses how your devices interact with the internet.
What your post seems to be saying is that the hotspot is giving inaccurate data. That’s not surprising.
Expecting your phone to have the same featureset as a security/privacy focused mobile router is a bit unrealistic.
You want something like this. That’s the only way you’ll meet your expectations:
An ultra-slim travel router that instantly extends your UniFi Network wherever you are, bringing secure, familiar connectivity to remote locations.
eu.store.ui.com
As for the time being, I wouldn’t trust the data coming from the hotspot app to be overly accurate. Monitor what’s happening from the devices themselves to get a more accurate picture of what’s going on. Get some dedicated system monitor / network monitor tools.