"But again this is the first production use of an overhead cam."
The Peugeot 500 M motorcycle of 1913 pre-dates this. Peugeot was also designing road cars to use it.
I also take issue with the "first aircraft designed to a Spec" and the "developed" claim. I think the DH.6 may be the first of the former (and other aircraft involved in RFC trainer requirements), and the latter applies to any aircraft which made it past first flight pretty much.
First V12 was 1904, according to the albeit dodgy Wiki. At least three more were developed pre-war and all can be claimed as 'production' engines (i.e. not experimental, and made in numbers for commercial sale). A definition of 'production' for the R-R engine would have to be based on some contrived criteria.
It's an interesting topic, but the "O" series should be considered as interesting and pivotal types without the need for hyperbole.