> I’m the team lead and I’m on the phone with my team members at least half a day every day. We definitely chit chat and talk socially as a matter of course throughout the day.

I chit-chat with colleagues too, but they're not work-friends because it's usually in the context of doing work (e.g. a few minutes of friendly small talk before we get down to business).

A work-friend is someone you go hang out with just to hang out or talk with just to talk. The main difference with a friend-friend is that doesn't happen outside of the workplace or work events.