GTP's don't make much high end RPM HP - higher RPM only equals higher MPH with traction but I think you are kinda on the right track imo anyway...
My take is that when spinning or losing traction, which sometimes results in higher trap speeds, is due to of all the energy in a spinning tire that eventually hooks & allows a car to avoid a portion of slower acceleration with perfect grip. Your ET goes to poop but you ended up hooking at a slightly higher speed which is turns allows you to hit a higher speed by the time you get to the last 60 feet of the track (where many 1/4 miles measure trap speed - avg over last 60 ft). There are also a million other factors that come into play as no run is exactly the same as another. I have actually had runs where ET & MPH were the best of the night in a single drag, even over 15 passes in a night.