I suspect (but am guessing!) that the smaller holes are putting proportionally more air in the turbine slots and at a higher velocity, and less air impinging on the outer metal surface of the rotor where it simply goes around the outside and out the exhaust?
Gas velocity is everything in the turbine. - And putting it where you want it, versus NOT putting it where you do NOT want it is the key to efficiency.
What was the pressure gauge steady at with the larger holes, and what is it steady at now?
K2
As the videos show, there isn't a steady pressure time period; when I open the valve to the compressor's air tank, all the air inside the tank rushes out through the nozzles. Tank pressure starts out at 100 psi and steadily decreases in just a few seconds.