Why do the NTSC and PAL color bursts look different when displayed on a waveform monitor?

Why do the NTSC and PAL color bursts look different when displayed on a waveform monitor?

The NTSC color burst looks like two sine waves layed on top of each other and the PAL color burst looks like it has a lot of jitter. The NTSC color burst changes phase 180 degrees from frame to frame so four fields are required to repeat the original subcarrier to horizontal sync (SCH) phase relationship. As a result, the burst looks like two sine waves laid on top of each other 180 degress out of phase.

The PAL color burst changes phase 270 degrees from frame to frame so 8 fields are required to repeat the orginal SCH phase relationship, plus there is an additional 1/625 of a subcarrier cycle shift for each line in the frame. Consequently, the PAL color burst creates an envelope that is completely filled with overlapping sine waves which gives the impression that the color burst has jitter.