Turns out that in school you make a whole deal about "being friends", but it really is as simple as being friendly with someone.
I overcorrected after having very few friends in school and now anyone who smiles at me is my friend and can be invited out for dinner or drinks. Everyone is happy to be invited at least, but I notice it's only the people who aren't expected home by their children will accept my invitations. They can still be friends, but it's a little difficult to build a friendship.
(I say overcorrected, but it's more that I have to take on a naive belief just to cancel out my autism a little.)