I know those boats were built in various yards and called by different names. Perhaps this phenomenon applies to the PT brand.
I have been aboard several that had been lengthened by as little as 3 feet and as much as 6 feet. All of the extra length was in the cockpit. The ones I was aboard were a Euro version of my own C&L44, ranging from 47 to 53 feet. The lengthening was done in each case after the boat had been shipped to Seattle or Vancouver. Only the hull was lengthened. The running gear remained in its original position, the hawse holes on the sides stayed put too. Still made a very nice improvement to cockpit size.