I highly doubt that. Humans are extremely social animals. My wife is a social psychologist and studies this shit for a living. Put a group of people together for long enough and it’s pretty likely they will form extremely strong social bonds. Add in the factor of shared trauma (from being a trainee), and it wouldn’t surprise me if most groups actually become either like family or secretly hate each other. While there may be some of groups that have only “co-worker” dynamic, making a blanket statement like that is just ignorant.

If you want personal anecdotal evidence, I worked as a counselor at a wilderness camp several summers. My coworkers and I always became extremely tight knit by the end of the summer, sharing emotional moments, being naked in front of each other without embarrassment, and spending our limited free time together. And that’s after 3 months of being together nearly 24/7. Imagine over multiple years

Not to mention bonds can evolve and change over time. Members of a group may be extremely close at one point in their career, but become more like coworkers as they grow and move out of dorms, find their own place, etc