Naw, I think he liked shorties for their less distinct, fuzzy, smearing tone - he was never into a really clean signal, even at a time when clean bass signals ruled.
In interviews he has said that he really doesn't like non-symmetrical bass shapes such as Fenders, Rics and I guess then TBirds also, he prefers doublecuts (his Punisher is really just a sleeker and elongated Grabber shapewise). His Axe basses are obviously an exception from the rule for show purposes, but has he ever played a whole gig just using the Axe?
But then Gene has never been that particular about his gear, which in my world speaks rather for than against him. I shake my heads at people who let the color of the pick determine whether they can get "their" sound or not.
PS: Goes to show how a Fender P looks crap even on the mighty God of Thunder in full regalia!
PPS: Get that stare right ...