Is the Glasswire mobile app for android a TRUE VPN?
Nope. GlassWire for Android https://www.glasswire.com/glasswire-for-android/ has an internal VPN, so your traffic never leaves your phone.
This VPN is off, and only on if you turn on the firewall feature. The VPN is not required to monitor your data.
Please note we can never see your data even if we wanted because it never leaves your phone and our app never accesses the network at all.
https://www.glasswire.com/privacy/
Yup it has its own internal VPN 
You do not have a Understanding of VPN. A VPN on mobile is used to secure and encrypt data going in and out of your phone. More info is here https://en.wikipedia.org/wiki/Virtual_private_network
Switzerland-based VPN provider offers an excellent Android VPN VyprVPN, A good mix of speed and security. But it is paid.