No, it's not.
Karnak and Kev are calling the symptom the disease. Cause and effect. They're listing one of the effects, not the cause.
The reason the CHOG was used so extensively was the ease with which folks could get kills. The power, performance, firepower, and all around capability of the plane itself lead to 20% use. The use was just an effect, the cause was the stats of the plane itself.
The Spit14 has never been unperked, ever, so you can't use the "wild and free" stats to relate directly to its capabilities, as it's never been "free-range" (so to speak).
The lack of use is just one effect from several causes. It is parallel to the perk status, not directly linked to it. Hence why he's putting the cart before the horse. The performance is not the sole indicator of use (as he's implying -- his argument is that it's not used so it must not be a very good plane, why perk it?). Among other things are the plane's name, reputation, word of mouth, the perk price itself drives away 90% of most pilots (it worked for the chog!!!!), and the availability of "almost as good" options that are perk free lead it to be glossed over. All of these causes lead to the effect of "low player use" -- and are not directly tied at all to the reason it's perked.
Aside from a few folks that advocate removing ALL perks, you can't unperk the spit14 without unperking the f4u4, chog, or the tempest.
And yes, I've flown it enough to know that it's worth the perk, which is a measely 15-16 perks right about now.
EDIT:
P.S. It was perked by HTC the second it came out. Thus it was NOT perked because of player use. It was given said perk before any use. HTC perked it before even seeing how "popular" it would be, so you probably can't claim player use (kills/deaths) is the reason to unperk it.