You could be right but it your on a long sweeping corner I'm sure you have more grip acceleration steadily or staying at the same speed. If you put the clutch in it feels like you have less grip.
As long as the wheels are in contact with the ground you will have grip. Grip is simply the friction generate by the tyre and the ground. This is determined by things like tyre compunction, temperature, road surface. You loss grip is the rotational force of the tyre is more than the friction been generated (wheel spin). You get liftoff oversteer in FWD cars because when you take the power off the front wheels all of a sudden gain MORE grip because they no longer have to accelerate. If the grip available to the front tyres is now more than that of rear tyres the car will oversteer.
Than there's obviously wait transfer, which changes alot especially when you have 500bhp. Taking the foot off the accelerator can shift the weight off rear tyres which in turn can REDUCE grip. But they will still generate grip just relatively less.
Am sure some one doing physics can correct me in much geared detail...I took one look at a mechanical engineering degree, saw the words Fluid dynamics and decided it sounded too hard so did something easier instead