I give the provider a little bit of benefit of the doubt.
It appears to be some generic “advice”, to an extent these are legit for following reasons:
- Some hotspot solutions do not mix well with VPN.
- Per-connection Mac Randomization prevents auto-connect feature of hotspots (they most likely rely on MAC address to remember you (so they would know you and let you connect)
- Some hotspot solutions also do not mix well with Private DNS features.
If I were you I would do a few more tests just to confirm the cause, and simply ask that company if they would do anything about it.
If they won’t and you don’t wanna compromise, you know what to do.