Your wording is "might be advantageous" to use less MP. For others it might be to have more MP. Canon does not serve the best for those, and the rest is you making word games.
1. Higher FPS? Canon offers lower resolution modes for years.
2. Better Buffer capacity? Canon offers lower resolution modes for years.
3. Better high ISO noise? Not for the same print size, and lower MP doesn't allow for higher print sizes, so this argument is rubbish.
4. Diminishing returns as more MPs means diffraction sets in at lower apertures - again, there's no loss for the same print size, and there's a gain with higher apertures.
5. Higher shutter speeds are needed or you need to use a tripod more often - same, as above.
6. High MP camera is clearly a niche product that is not a high priority for Canon - its high enough for Canon to actually make such sensors, which go into real cameras. Not the type you're talking about, but some have actually seen one, which means they think is "the best."
Next time, feed your straw men to donkeys.
I have real argument, you're just not worth the effort of making it, because you're not as clever as you think.