Nah, not necessarily. Back in the day (I may have mentioned on here before that I used to have long periods...I'm talking 19 days...), I was camming on MFC, and for whatever reason I had my back/body facing away from the webcam doing something. When I turned back around and sat back in my chair, this MFC member kindly told me that I was bleeding. I looked down, and sure enough...there it was. And I assure you I would never put on a period show in public chat.
Not every woman is the same. Also, I used to get very long periods. I'm talking 19-day periods. That's the reason I was put on the birth control pill. I could not take that shit anymore.....
If it's really true about cam sites penalizing models for accidentally getting their periods while on cam, I wouldn't be surprised if one of those sites was Cams. Lol. I can't tell you how many times I've been suspended from that site. I'm just coming back from a suspension, in fact. Haha.