I am finding all of this to be so true! Granted, this is only my second year hatching peas, but your point is not wasted on me as I just brought in 30 eggs that have been under broody chickens and are due on the fourth, well that would be 28 days. Of the thirty eggs I had not candled them at all until tonight and only had three clears, all the rest except for one had developed and showed internal pip. That one looks good but I did not want to let them cool so I did not watch if very long for movement.
I also have a tray of 42 that were set in the Sportsman at the same time, I did candle them about a week ago and removed 10. Of the 38 that I just candled to move into the hatcher only 6 had movement. That is the worst hatch I have had in the incubator yet. The only thing that is different in the GQF from previous hatches is that the humidity has risen to mid to upper 50's for over a week with no changes by me. It had settled down to mid 40's this past week.
I am now employing 17 broody chicken hens much to the dismay of my wife. She is not liking the drop of egg production in her flock.
Those overly large chicks you mention take a lot more help to get out of the egg, and if timing isn't right they don't make it out alive.