Unless you actively pay attention it’s very easy to be logged into some Google service without noticing. At least I wouldn’t be surprised if chrome background services kept me logged into my work Google Mail account and kept tracking my IP.
The biggest question is how meaningful the IP alone is. I don’t know if VPNs assign people individual IP-adresses or if there’s some kind of NAT in use where people share an IP with translated ports. If the information is “there’s this individual VPN-user and we need to connect them to a name” then you shouldn’t use (the same) VPN for everything, but if it’s just “there’s another request from the same VPN” then it’s fine.
And which country are you from that you think you are entitled to throw the first stone?