I don't know of any "credible" source that would lead you to believe that. If your source isn't credible, then it's usually a good idea to actually check before accepting these things as facts.
It takes only one good look at each of the two engines to realise that there is no similarity of design at all.

The BMC engines, for some wholey inexplicable reason, run the ports back between the pushrods while every other production inline OHV engine design that I can bring to mind runs the ports out to the other side of the head without needing to compromise the shape, position or number of ports as a result of pushrod positioning.
The British engine, [& the Datsun copies] use two inlet ports only in their obsolete iron heads.
It's this reversal of port layout that places the exhaust manifold over the fuel pump & provided road service organisations throughout Australia with a large workload during summer when vapour lock problems plagued Austin cars & trucks when heat from the manifold turned the fuel pump into a fuel cooker. [Morris cars used an electric pump]