I’ve never heard this mill story. Primanti’s was a restaurant in the strip district that serviced truckers and was open all night but not all day.
I went there after concerts at Heinz Hall. I remember standing in line with other concert/theater goers and the truckers until the doors opened around midnight.
Neither did I, it seems like some millenial made it up from whole cloth.
The strip was always produce and flowers.
I never heard the mill story either. Always heard it was for the truckers, which makes more sense. My dad worked in the mill and my mom packed his lunch. All the mill workers I ever saw brought their lunches from home. There was nowhere to actually go eat (I think there was a small shop for sodas and coffee where my dad was) and no one’s lunch time was long enough to actually walk all the way to the parking lot off site, and drive somewhere to go eat, and get back in time. In fact “lunch” was pretty much whenever one had some down time between tasks to go to the shanty and eat.