I shoot all the time at 60P but my shutter speed is always 1/60. So I have the motion blur of 30P at the classic 180 shutter and can extract that frame rate anytime from the timeline if I choose. ( I don't because I like the 60P motion) Your argument is exactly why I shoot this way. I have never followed "the rule " When I shot 60i it was also at 1/60. Please don't say that is correct for 29.97i as there are 59.94 fields a sec to expose for individually and the same temporal motion as 60P they are just fields not full frames so the exposure parameters are the same.
My understanding of "the rule " was to avoid shutter speeds that were too fast which would accentuate the artifacts of a slow frame rate such as making judder more pronounced etc Likewise the shallow depth of field was also to hide the background judder etc. Lots of rules need to be followed to make a good viewable 24P film. These approaches are also good practice on frame rates without the issues too. I shoot with 3 cameras at 60P and rarely pan or zoom them for inclusion in finished piece. Now with UHD going to a HD final the crop/pan and zoom can be done in editing without those artifacts and much smoother and timed to the event much better than I could ever do manually.
