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Actually, it's Brazil that has "PAL M" - same scanning standards as NTSC, but alternating phase by line. By the way, it's the R-Y that switches phase. The burst has a R-Y component in addition to the -(B-Y) component, causing it ot switch phase +/- 45 degrees. The alternating phase makes a comb filter for luma very difficult to accomplish, since the phase alternation makes the (R-Y) line up from line to line, just like luma. To get away from this, PAL also offsets the color subcarrier slightly so that the phase of both R-Y and B-Y cancels from frame to frame.
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