That would be an application of the Bernoulli theorem, but yes, that would be the expected result.
Factory yes, but which factory and where? Most certainly not the Jaguar factory at Browns Lane, Allesly. 
(And not the old factory nor experimental department at Foleshill, Hollbrook Lane, Coventry either)
It’s amazing how often these creations emerge. I am sure it will be very easy to get a JHT certificate and I put my money on that it says it was a perfectly normal XK120 OTS SE (or SE) if you are lucky!
There’s a less imaginative version in Finland that has a chassis number from a FHC. 
Very rare, I bet.
Cheers!