Scenario below:
Clear previous friend list. Completely empty.
Turn on auto-add
Play two 1v1 games, now have 4 'friends'
Two are opponents, other two are complete random people who I have never played and did not manually add

How does this make sense?

Did they create the games you joined? If it's created by someone without joining it themselves it can be easy to miss.

Were the games you joined open games? Someone could have joined an open seat and then left, and you might not have noticed.

Nope. Both games referenced were created by me. Certainly is possible that they could have joined the open seats before leaving... didn't realize that would add to the list, figured it only happened with the start of a game.