Notice that the M5 has much closer gear ratios (5.1 to 2.6) versus the V's wider (5.3 to 2.1) range, so for raw performance, the M5 is more optimal.
Notice also that in 4th gear, the torque multiplication factor is 4% better for the M5, so the 1-2% advantage for the 1:1 higher efficiency in the V, should still give the M5 a slight upper hand, but in real life, the V pulls the M5 in 4th.
Now if you look at the chart for optimal V shift points:
You can see that both 2->3 and 3->4 are SUB-optimal in the V with a factory rev-limit of 6600rpm. So the V is making a huge ratio jump in the 3->4 shift and dropping out of the power band from 95mph to about 105, yet Jim claims that he is still pulling away from the M5 at this point (up to 110).
The speed in gears makes this a little more obvious:
And you can see that the MOST optimal shift in the V is the 4->5 shift, because instead of dropping out of the power band, you make a short ratio jump and end up starting 5th at 5500, putting down the same 340 or so whp that you were in 4th. I.e. you don't take a hp drop like 3rd-4th, which starts out back at 275whp or so back at 4500. So simply put, the V is really at the top of it's game from 100-160mph, and if you haven't pulled ahead by 100, there is little chance of getting it back.
Looking at that last chart, it is pretty clear why the V is no high speed record holder.... 6th gear is simply for highway mileage not top speed runs. In stock form, there just isn't enough power down below 4500 rpm to mount a charge towards the 180mph mark in 6th gear.