the precurve only helps a bit, the problem is the thickness of the glove makes your grip tire out instantly. think about this, if the precurve really helped you grip the bar, you could put a glove without a hand in it, just the plain glove, on a bar, and it could tug the bar enough to turn the kite. Precurve gives you maybe an ounce of pressure, and we are gripping these bars with somewhere between 5 to 20 pounds....
I don't think that's the point of the pre-curve (to provide grip). The idea is, since the glove is already bent you don't have to stretch the material on the top of your hand (cut off circulation) and bunch the material on the inside of your hand (additional padding creating more fatique) when you bend your hand on a non curved glove.
That's my view on it anyway.
This. My new XCEL Drylock gloves require a reasonable amount of effort to just bend the fingers
used my old 5mm gloves yesterday... timed my tacks so when one forearm tired, I'd go the other way