That's a great question.
The pace projector is based off of past pace figures and running styles.
Blinkers are generally a speed enhancer and can sometimes fire up a horse early on, but they come in different cup sizes and it's very tough to quantify how much of an impact they will have on a horses early speed.
The pace projector is nice because it gives a quick and clean look at how the pace is expected to unfold based on past data... but it does not take into account the human factor or equipment changes like 1st blinkers. That part, is left up to the bettor.
The human factor is the other main thing that's hard to quantify. Jockeys, either by their own choice or by trainer instruction, can hustle a horse early and get it to show uncharacteristic levels of early speed. Just as they can grab a hold of the horse, and rate it along through the early stages, going much slower than it typically would.
If a jockey/trainer thinks that a race is paceless or thinks that the track is speed biased... they're more likely to ride aggressive early. In situations where the pace figures to be contested, and the strongest horses are mid-pack or closer types...you'll often see multiple jockeys trying to hold their horses through the early stages.
Basically, the human factor and equipment changes are left up to the bettor.
A great example of the usefulness of the pace projector in a high profile race just happened with the Queen's Plate last Sunday:
At just a glance, it was crystal clear that Midnight Aria was projected to be absolutely isolated on a loose early lead. As it turned out, he was able to glide along on a loose early lead with no pressure. Midnight Aria parlayed the perfect trip into a wire-to-wire win at 16/1 odds.
