It’s for TV purposes. Reality is not a concern.
There’s a lot of fudging things in the show concerning it’s size, staffing, etc.
It is supposed to be a nationally ranked teaching hospital. But, the main exterior building shown is a small 3-story VA rehab facility. The elevator numbers, though, go up to 5. There is only one small surgery floor for all departments. And only two ORs shown in the early years. With OR numbers going up to like 12 shown on the OR schedule board.
This wouldn’t even be a top hospital in Seattle, let alone the nation.
At the beginning, the ER and its residents were treated as a different group. That went away so that there could be more “action” for the surgical residents.
For a while there was even a clinic for walk-ins that was manned by the surgical staff for some reason.
Occasionally, other departments have a person or two show up. Psych had a resident that showed up a few times. Some interaction with neonatal including one resident that was shown a whopping 2 times, etc.
I’m not sure if anyone ever labeled “General Medicine”/“Medical” has ever been shown. (At least Scrubs maintained the distinction.)
Once in a while, the CoS calls people together to make a big announcement. Usually this is from a set of stair to a lobby full of people (surgeons and nurses). Can’t be more than 30 people at a time. Once, it was to surgeons in an OR. Something like ~20 people. A few times, there’s a big meeting in an auditorium, so theoretically 50+ people but I doubt that many are shown.
If you’re paying attention to anesthesiologists, watch carefully in Season 1, one of them later turns up as …
The problem started with the pilot. They said that there were 6 women among 20 surgical interns. 3 were regulars. But at least 5 other women are shown during the episode.
Counting, consistency, are not an issue on TV. (E.g., the recent return of you-know-who episode mentioned the “last 7 years”, when it’s only 6 within the show.)