Actually, the voltages had to be raised due to the shadow mask, and this rise in voltage meant you were now in x-ray territory, which wasn't the case before. The infamous problems with TV's emitting x-rays and associate recalls were the early color TV's. And it wasn't so much from the tube, but from the shunt regulators etc. in the power supply that were themselves vacuum tubes. If you removed the protection cans around those you would be exposed to strong radiation. Most of that went away when the TV's were transistorized so the high-voltage circuits didn't involve vacuum tubes.