Sorry but you are wrong with respect to current/horsepower going DOWN at
high pressure.

I only know what the meter says. There may be some kind of unloader in there
but I really think it is just that it can't take in any more air.
This is the C/H diaphram oilless compressor with a 6.25 sticker and a 1HP
motor. In the middle of the range it actually draws more than the labelled FLA,
then tapers off. That was the day I bought it.
If you have the January archives of this NG, I posted the actual curve