So I haven't seen this video, likely won't watch the video, but another thing besides periods/birth control stuff is something known as a friable cervix. It's the fancy way to say a cervix that bleeds or has inflammation easier than normal. A fingernail scratch or dildo inserted too deeply too quickly(the cervix moves during arousal to allow the vaginal canal to get longer) can absolutely cause a friable cervix to have spotting or a little bit of blood now and again. It's no big deal and can be caused by everything from STIs to birth control to IUDs to thyroid issues.
I wouldn't be surprised at all if this was what was going on. Katie has had this happen before in the past, including in some premium content.