Give me the benefit of the doubt here and say it does take 2 seconds longer to insert a cam as opposed to clipping a bolt.it takes me MAYBE a second or two longer than it does to hang a draw and clip it.
2 seconds x 10 gear placements (give or take a couple) = 20 seconds longer that your muscles are contracted on a route. Considering the route may take 5 minutes this is harder because your muscles are becoming fatigued even if using relaxed placements.
Dont believe me? Do as many pushups as you can, don't forget to keep count. Wait 5 minutes and try again this time stop 1/2 way on the way up and count one thousand one, one thousand two before finishing the rep and continue. Be sure to pause 2 seconds in the middle of every rep to mimic the additional time needed to place gear. How many did you get? Probably less.
The fact that your muscles have to contract for a longer period of time makes it an itsy bitsy, tiny, miniscule amount harder. Saying "if anything it's easier" is just plain ridiculous.