Yup, the tube and tyre rub against each other as they are deformed by whatever it is that your rolling over, dissipating energy. This effect gets worse with lower tyre pressures as the two bits of rubber stick to each other less and rub more.
As the friction occurs at the edge of the tyre, you have in effect a lever ~35cm long in comparison to a lever ~2cm long due to your hub friction. As far as I understand, this is why you can have lower rolling resistance using tubeless compared with tubed, even with lower tyre pressures.