Comment by layer8

PWM still counts as sample-and-hold, because it sustains the brightness throughout the duration of a frame, resulting in significant motion blur. The converse are impulse-driven displays like CRT and plasma.

LED backlights using PWM likewise don’t change the sample-and-hold nature of LCD panels.

My understanding is that PWM switching costs aren’t negligible, and that this contributes to why PWM frequencies are often fairly low.