Worked With is different from Friends, on purpose.
A friend is a social connection. Someone asked, someone accepted. It says nothing about whether you have ever worked together.
Worked With is a fact out of ATOM's own tour rosters: you were on the same tour. Nobody accepts it, nobody can claim it, and it cannot be padded, which is exactly what makes it worth something professionally.
It sits on your Friends page as a collapsed drawer, showing each person, the tour or tours you shared, and whether you are actually connected. That last part is the useful bit: people you demonstrably worked with but never added.
WHEN YOU JOIN A TOUR: right after you accept a tour invite (or sign up from one), ATOM asks Add your tour mates? and lists the people on that tour you are not connected with yet, all checked. Send friend requests sends them requests (each person still accepts); Not now skips it. Tours you were invited onto count, not just your own.
PRIVACY: it only ever reads rosters YOU are on. It cannot be used to look up somebody else's crew. Blocked people are filtered, and closed accounts do not appear.