The claim was found in an aviationist article not unlike the one that you quoted. There is no actual reference to specific simulation other than it was based on a simulation and so one would have to view such claims with a degree of scepticism depending on your own personal leaning on the F-22's capabilities. There will never be anything official other than actual combat statistics.
Well gents, that is a true story, around the time that Langley was converting to the F-22, one F-22 took on 8 F-15s and defeated them all, as they attempted to defend their airspace against the F-22. I have read this same story in multiple sources with no variation on the theme, and I do believe it is a very up-front mano-a-mano beat down. I did a quick search for it and so far I can't come up with the original credible source, but I believe it was published as fact in the Air Force Magazine!