Well, I think it comes down to his ability as a rider. A 600 SS is usually capable (with an EXCELLENT rider i.e. magazine rider) of high 10s.
A Honda liter bike (actually the Honda inlines are 919cc, 929cc and 954cc) should be capable of low 10s at least, especially if he's claiming its worked.
Also, the weight factor: In 2002, the dry weight of the F4i and the 954RR are the EXACT SAME: weighing in at 370 lbs dry...
Here are some cold hard figures from MotorCyclist:
Honda CBR600F4i: 10.71@126.7 mph
Kawasaki ZX6r: 10.92@124.4 mph
Suzuki GSXR600: 10.69@126.6 mph
Yammy R6: 10.75@126.6 mph
Honda CBR954RR: 10.2@139 mph
Kawasaki ZX9r: 10.16@138.28 mph
Gixxer 1000: 9.89@145.35 mph
Yammy R1: 10.07@142.13 mph
.
The excuse of the wheels floating is somewhat acceptable if he means wheelieing at the line, but then he should know enough about his bike that he wouldn't be setting up races without equipping the scoot specifically for drag racing. If he means the wheels are floating down the track, the 600 actually has a longer wheelbase than a liter bike, allowing less chance for a tankslapper.
Ask 1fastchick, last time I heard, she was running at least low 11s with a STOCK Yammy R6...Since your GT is not heavily modified, I'm guessing that you should be running high 13s correct? Then he should have been way ahead of you! Get that boy to an advanced MSF course
BTW: I'm totally flattered that you asked me
There are several other peeps on the boards that are WAY more knowledgable than I, and I hope they come forward in case I missed something!