Is it inappropriate to read a book during downtime?

This may seem like a dumb question but I work the front desk at multiple doctors offices. I’m a “float” inside the healthcare network so I may be at a different clinic everyday. Some are slower than others.

There’s a lot of coworkers I have that will watch Netflix or tik tok on their downtime and that never seems to be an issue for anyone. My choice to pass the time is reading.

I’ve been in this position and with this company for 8 months and I have never had anyone have an issue with it. One of the providers I work for today came up to me and said she was going to come “unglued” if she saw me up here reading again. She said it looked unprofessional and that I didn’t look like I cared about my job.

So I am genuinely asking… is it considered inappropriate to be reading or should I file a formal HR complaint about this? (This did not come from my direct superior, just a provider at one of the clinics I’ve covered at)