If you were to ask Tim Tackett about Paul Vunak, Erik Paulson, Joel Clark, Ron Balicki, Rick Young, Yori Nakamura........... he'd tell you they are all very good and tough guys. Any of them without a shadow of a doubt are more complete martial artists and more knowledgeable than people like Tommy Carruthers. Whilst people like Tommy Carruthers will tell you defences against grapplers, knives, etc, people like Ron Balicki, Joel Clark, etc have learned it all to a high level and worked against skilled practitioners some of the best in the world. Saying just strike or bite if taken down and get to your feet quick that Tommy Carruthers advocates, people like Ron Balicki, etc have actually worked with the Gracies and the best grapplers in the world to know in functional terms what works and what doesn't especially against someone with even decent skills. Same for knife or anything else, training against a skilled Filipino martial arts practitioner raises your game. People doing mainly or only Tommy Carruthers Jeet Kune Do version, Carter Hargrave Jeet Kune Do version, Traditional Wing Chun, George Dillman's Pressure Points...... will be in for a real shock if they face anyone experienced in MMA, as they train mainly to deal with an untrained person. Throwing flicky finger jabs and side kicks won't stop or surprise someone highly skilled in MMA. Many MMA people have street fighting experience also and these days, the chances of facing people on the street trained in MMA or other arts has increased since the 1950's or 1960's.
Tim Tackett in that quote you gave, mentions Tommy trained there for about a week, and that he also visited his school once in U.K. which again begs the question where did Tommy Carruthers learn all the Chinatown Jeet Kune Do syllabus? As it has a lot of material such as the trapping. Jesse Glover and Ted Wong did not know it all. Regarding Tommy Carruthers skill level it is obvious he is not that great or a fighter but that does not matter he enjoys doing what he is doing and his students think he is a good teacher, Tim Tackett I don't think was ever anything special even in his prime or an exceptional athlete and that does not matter either he is a great teacher and Dan Inosanto himself has said he is one of the most knowledgeable Jeet Kune Do people in the world.