I'm not sure I understand this completely.

Would this help with the problem of horses of different quality finishing at various rates of speed at the end of a race or do they already account for that?

For example, do they accurately capture the difference between top turf and dirt horses when they give us beaten lengths?

Good turf horses routinely run sub 12 second fractions in the last furlong while you rarely see that on dirt. That should somehow be built into the beaten lengths.

Of course if we can get the actual times, then that's much better. Good luck with your effort.