Unfortunately, I have to agree. I tried to do what Rosanna did too: sign up without using my Facebook or google account. So I did, only to then find that they had connected to my google account. I could see this, because they used my profile pic. Think it is probably a mix between the settings on my browser (chrome) and the choices made by this site.
To me, that is not a problem, but it is something to be aware of.