The biggest advantage didn’t come from using the H shifter alone apparently, there were/are tricks/glitches in the way people were using it that made it even faster than it should have been. People could switch back and forth between shifter and paddles constantly for the quickest shift. From what I’ve read people using these tricks would downshift with the paddles because it was faster and eliminates missed gears, but upshift 1-2 and 2-3 with the shifter because it’s faster than the paddles shift, but shifts 3-4, 4-5 and 5-6 would again use paddles because the game simulates those shifts fairly quickly in most cars and it removes the chances of a missed gear.
But this it where the real trick happens, most cars have one shift that is the slower than the rest, in a lot of cases it’s 1-2 or 2-3, for this example let’s say the cars slowest shift is 2-3. Here how it works, your in 6th gear and coming to a hairpin, so what you could do was downshift with paddles to 4th, then downshift to 3rd with the stick, then use the paddles again to down shift to 2nd from there for the corner leaving the stick in 3rd, then when exiting the corner instead of using the paddle or stick(because this is the cars slowest shift) to upshift you just hit the clutch and because the stick is in 3rd already the cars skips instantly into 3rd, eliminating the slowest shift, then use paddles again the rest of the way to 6th.
Or from the standing start, again we’ll use shift 2-3 as the cars slowest shift. Before the start you put the stick in 3rd, then downshift to 1st with the paddles, race starts and you take off in 1st, use paddles to shift to 2nd, then when it time for the slowest shift to 3rd you again just hit the clutch and the car jumps to 3rd near instantly and you shoot ahead of others using paddles/DS4’s.
PD should have nerfed these glitches, not the clutch/shifter.