Without pressure there would of course be no velocity. Pressure & velocity are thus directly related. What is so seldom mentioned & so seemingly not understood is pressure involves a Whole lot more than just the maximum peak pressure. Pressure as it relates to velocity includes the "Total Pressure" from breech to muzzle, or everything under the curve.
A higher pressure thus gives a higher velocity, but this "Absolutely Does Not" say the load giving the highest "Peak" pressure will necessarily have the highest velocity.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra