Does a factory reset not log you out of all your accounts?

Hello community!

I traded off my iPhone 7 Plus beginning of 2023 when buying a new phone on Amazon. Before giving it away, I did a factory reset to wipe everything from the phone (I probably did it twice).

My Google account has 2FA setup. However, today when I opened the Your Devices section of my Google account, I saw that my account was still online in my old phone:

How is this possible? I don't see the same for my other accounts that were also present on the same phone. I never got a security alert either about this login.

Once factory reset is done on iPhone, it is supposed to erase everything permanently, and logging back into the same account that existed on the device prior to reset should still ask for password and 2FA code, isn't it?

I'm a bit worried because this is my main account.

TIA