As mentioned in the website, rotary valve cylinder heads have been around almost since the invention of the infernal combustion engine.
Dunstan Engineering in South Australia made some single shaft versions for the old Holden six cylinder engine in the late 50's & early 60's. I believe that it was the third version that had a front drive that allowed the engine to be used in a car, previous versions being used in boat applications.
They were alleged to be good for 12,000 rpm which is when the rods stretched. [that's about 60mph/100kph in first gear of an old Holden]
A friend in a nearby town has one of these heads but all of the previous efforts, including the Dunstan ones had the same basic problem as the sleve valve engine, the sealing in of combustion gasses & of oil after a relatively short time in service.
If this mob has actually overcome that problem then the days of the poppet valve could well be numbered in new car engines.
Dunstan link