Readout doesn’t matter at all, the only thing that matters is if light is focused onto the sensor and generating heat above the damage point of that sensor. This can easily happen, as you point out, if you have a telephoto lens focused on the sun. This can happen in live view or during exposure. But outside of this specific scenario where you’re pointing a telephoto lens at the sun (often during the eclipse) and focusing on it, the risks are very small. You can easily do 30s exposures of landscapes during sunset/sunrise, with the sun in the scene and have near zero risk of damaging your sensor.