All the Whitworth's I've seen are built from P14's.
Surely he's referring to the Interarms Whitworths made with the Mk.X Mauser action.
You're probably right. I've never seen any with Mauser actions here, but that could be that they weren't really being sold much around here by the time they were building them from Mausers. Or maybe it's because I only noticed the Enfields, being "an Enfield man myself."