I just realized that if you try to maintain a "true" 525-line interlaced system in the conversion, you'd have to use the fields out of sequence.
Let's say field #5 has just arrived and you need to make the odd field of a true 525-line frame. You'd combine fields 1 (blue), 3 (red) and 5 (green), all of which were odd.
Then when field #6 arrives, you'd make the even field by combining fields 2 (green), 4 (blue) and 6 (red), all of which are even. But notice that not only are you building each NTSC frame out of fields that span twice as much time, you have sent green field 5 before green field 2! That would make the color confetti problem even weirder.
The whole sequence would be something like this:
blue green red
1 5 3
4 2 6
7 5 3
4 8 6
7 5 9
10 8 6
7 11 9
10 8 12
13 11 9
10 14 12
13 11 15
16 14 12
13 17 15
16 14 18
...
i.e., use three consecutive blue fields, then step one back and use three overlapping consecutive blue fields, etc., with interleaved phasing for the other two colors. What a mess! The only practical way to do this would have been to slow the color wheel down to 30 Hz, i.e., to make a frame-sequential color system. And you'd still have twice the time spread between the individual colors making up each NTSC frame.
So now I understand what you meant. They did turn the interlaced 525-line 30 Hz frame rate camera into effectively a 262-line progressive 60 Hz frame rate camera. And since alternate camera fields start half a line apart, you'd have to delay one by half a line to match the other (I forget whether the odd or even field starts in the middle of the line).
Interlacing probably seemed like such a good idea at the time, eh? Now it's just a major headache...
(Edited to add frame sequence examples)
