Earlier today I had to add someones's Google account to my Android phone, to help them with something. My phone is a Samsung Galaxy S7 with the latest Android version, not sure if this is important. Anyway, I helped them and then immediately removed the new account from my device, the whole thing took 4-5 minutes at most.
Now, I know that when adding a new account Google tries to download things like contacts from the new account to the phone, but does it also try to do the opposite? I mean, upload any information from other existing accounts on the phone to the new account?
The other person does not have my login details and I use two factor authentication.