hondaodyssey

I was recently informed at my institution that network engineers now have the ability to detect the user of a VPN signal. For context, people here are using free vpn apps such as Hexatech to gain access to otherwise blocked websites. Network admin says this is illegal based on their rules. They have said that even on a VPN it is possible for them to identify device details such as a MAC address and then trace it back to the user. Is this possible?