I am not a skeet shooter but have found that its more of a social type of shooting and a lot more relaxed than Trap so you tend to be more relaxed and have some fun ... The third round of skeet I shot as an adult I ran them (25) after shooting a 19 and 24 on the first two rounds ... WPT ... (YAC) ...
I never thought of trying sub gauges but can imagine there would be a hell of a difference .... I was shooting trap loads on the rounds I shot, don't recall if they were 7'5 's or 8's but it was fun ... WPT ... (YAC) ...
My high score in Skeet was 73/75 with a .410. I find it hard to stay focused in skeet far more than trap. I suppose I get bored easily.
I see the difference in focus as a difference in the timing of flipping the focus switch. When is one required to focus? Skeet has those eight stations with room for only one gunner at a time. When shooting on a full squad; you can get in plenty of relaxation while waiting for your next turn on a concrete slab. One should take advantage of the down time. Let the act of taking position on the station be the cue. Trap presents more of a focus challenge. One is always on a firing station except during a change. There is a danger one will remain too focused for too long a period. One needs to develop a personal cue about when to hit the switch. Think of the batter in baseball. He can afford to be relaxed in the on deck circle. He can afford to be relaxed between pitches.
It has always been more of a challenge for me to stay focused in trap rather than skeet. I tend to agree with Par4's statement above.