Basically, they just want you to check in and then they scan your health insurance card or receive whatever reports or body fluid samples you were supposed to bring. Maybe draw some blood, too. After that, there’s no need to warm a seat amidst a bunch of coughing people.
When I was a child and we entered a completely stuffed waiting room, my mother would turn around and ask the receptionist how long the waiting time was and if we could run some errands, and it’s never been an issue.
As an adult, I’m doing the same. I might buy and eat breakfast, or just walk around outside if the weather is nice.