I heard him say the same thing, and I spent a bit of time playing with the concept yesterday. Jury is out, still.
One tool I am using in dry press is a pulse laser cartridge (G-sight, but anything similar will probably suffice), where I will turn the red dot down, pick a spot on the target at about 20 yards (in relatively low indoor light conditions), focus hard on the target spot I have selected, and press the trigger. The laser dot should appear in a consistent location relative to the red dot if the press is correct, and should not traverse in any way. If the laser creates a streak, it’s easy to see which direction it streaks to (supplementing this with an iPhone app which tracks the laser dot and shows the vector, if any).
I have also found this useful when practicing a DA press with my iron-equipped P30’s, but again, target-focused. Very subtle finger position and press rate changes make for a substantial effect at the target.
These exercises are working out well for me in live fire practice.