My site has this enabled and Visible to set to Anyone so not this also.

As I stated earlier I'm thinking this is a bug!

The main UNA.IO site has the same behaviour. If you have a Standard account on UNA.IO and view another member and see Access denied (because their Profile is not public) then there is no Follow only Add Friend.

If you see the profile details (their profile is Public) you see both Follow and Add Friend.