Okay, I'll wade into this topic - fully prepared to be shot down. Fed the horses, nothing to do for the next hour.
US data compelling, although I am presuming, in all cases, the track/surface preparations are as close to perfection as could reasonably be in practice. Otherwise, the data would be meaningless. IMO. [ and I'm no statistician].
In our case, here in NZ, we have no comparable data, or none that I have seen anyway.
We can remove dirt as one parameter as we don't use it.
So, we have synthetic, which is ALL polytrack with no Tapeta as an alternative to compare, vs turf.
Is the synthetic presented at its optimum? do we have any idea wrt that? there is already evidence from the Kempton Park conversation, that the 'top' is 50mm less here than there, for example; and turf, with variations ranging from rock hard, shifty, too much grass, not enough, slippery, rough, full of holes, patchy, wet, gluey, sticky, heavy, bottomless and combinations of the above.
How that can be assessed or compared with any accuracy is beyond me.