Yeah, you’re pretty much right. Interlacing complicates it a bit more because not only would the previous frame “fade” but half of the frame was drawn, every other line, and then the next half. So it didn’t look like a flicker because it was basically 60fps for half of the total screen, but an alternating 30 frames for each half of the image. This is why on early and terrible transcodes, you can get a “comb” effect, it’s not properly combining the image per frame and showing you half of the last frame and half of the next frame and the motion in the image shows in combs.

It’s really interesting stuff, imo.