Unfortunately there doesn’t seem to be a way to link to a filtered set of reviews on the play store, but If you go to the store, find the app, go to the reviews and filter by 1 star you’ll see them. Some of them just don’t understand how the app works, as you say, but there are a number that are harder to ignore. The thing ism if it is acting as a pseudo VPN, it could easily leak when the OS suspends it (for power saving, switching network modes or the like). Honestly, I haven’t tested it, it doesn’t do what I need (I’m on another VPN a lot of the time), and I wouldn’t trust it very far myself, but if it does what you need, that’s what matters.

I personally observe with my own eyes many many times where Android turns off Adguard’s VPN for a split second when doing various Google things like receiving messages in Google Messages.

I haven’t been able to pinpoint it but my observation is that the disconnect/reconnect happens when a connection is trying to be made (ex. RCS message incoming), and I suspect Android is dropping the VPN to make its own connection. Sounds paranoid, but I’ve been carefully watching it happen for a long while.