Is Google aware of multiple user profiles sharing the same Android device?
If your Internet provider uses IPv6 and your device is using IPv6, and you use any service or web site that uses Google resources/services in any way Google can identify your device by it's IP address if you switch the profiles without rebooting no matter what ROM you have installed.
As modern devices with Google PlayServices + PlayStore installed contact PlayStore for updates even if no Google account has been set-up on one of your profiles.