Think about what's going on.
The mass going into the cylinder is the same, but it's not heating up as much.
What's different about a pound of air at 1,200 degrees compared to a pound of air at 1450 degrees?
BTW, I just looked at a bunch of midget and Sprint car cams, both my designs, and other cam companies designs. The biggest spread I found was 8 degrees at the seat(SB2 headed midget). The shortest was a zero spread(D3 headed midget).
The mopar sprint engine I was looking at had a 2 degree split from another cam company, and I mine was a 4 degree split.
Jones Cam Designs