They wanted to faithfully replicate Glaub's actual '64 P bass. The default P bass profile in '64 was wide and flat, aka a "pancake". Of all the L-series P basses the '64's seem to have been the most notorious for being uncomfortably wide at the nut. My '64 was the same way...uncomfortably wide. My Skyline Glaub was, too. When I got it I recall thinking "yep, feels just like a '64 Fender." Two weeks later, sore wrist.
My theory on, at least, one of the reasons why the Lakland USA Glaub necks were so uncomfortable was their 10" fingerboard radius along with their wide and flat contour. It's probably bad form as I am a self taught hack on my best day, but I often loop my fretting hand thumb over the fingerboard and the neck felt sharp against my hand. If I'd gotten the J width neck option on my USA Glaub, I probably would have kept it as it was a fine, fine, superfine instrument otherwise.