I've been curious as to why this is so widely believed. Most studio models handle their own chats. From what I understand, monitors only come into play when the model is unable to interact with chat herself or the chat is way too busy for her to keep up, so this would only be for bigger models. Or when assistance is needed with translation, but there are so many integrated translation tools anymore that the latter case isn't really necessary anymore.
A lot of the studios that models work for give you a room and the equipment, take half your money, and that's about it. The models provide their own outfits, toys, get limited tech support and often rely on other models for technical issues or assistance configuring the software, and are responsible for cleaning their own rooms.
I'm not sure if the eastern european studios are different, it sounds like they might be more actively involved in what their models are doing, but this recurring idea of "when you talk to a Colombian model you're actually talking to a monitor" doesn't seem to bear out in most cases.