As Katinas wrote earlier, nor his engine, nor the Ryger has auxiliary exhaust ports because those would require a wider piston skirt, that would in turn hamper the flow into the transfers. Since I read it here, I can react without endangering my NDA (thank you Katinas). And what follows now, is purely my own guesswork since I never received any relevant information from Ryger.
From the Ryger homologation papers we can see that the exhaust timing is lower than the Aprilia RSA timing, so the Ryger's blowdown angle.area is tiny compared to the RSA's. And when taking the initially quoted maximum torque rpm of 17500 into account, the Ryger's blowdown time.area was almost non-existent. It nevertheless did not stop it from producing over 70 hp.
And before anybody says that they've never seen any proof of this amount of power in the form of a real dyno graph, let me say that neither have I, but I was lucky enough to get a seat-of-the-pants impression of the original Ryger prototype before problems with the production engines brought the operation to a halt, and my pants are not that easily fooled, having ridden motorcycles with several hundred hp.
By the way, what made me decide to step out of the project, was the lack of frankness. I would have loved to take part in the development of that engine, but it turned out that I was only recruited to generate publicity. I'm sure I could have prevented some of those technical problems if only there had been an exchange of thoughts, but all I ever got were promises. It's a pity....
OK, back to my theory. Seeing that the in-cylinder pressure of the RSA is about 12 bar at exhaust opening, and given that the Ryger is claimed to produce about 20 hp more than the RSA, and given that the Ryger's blowdown time.area is so much smaller, there must be a huge amount of spent gases that enter the Ryger's transfer ducts, raising the pressure in the sub-piston volume and the density of the mixture (well observed, Philou). The higher pressure may lead to a much faster transfer flow, with more mixture inertia. This inertia then ought to pull more fresh mixture through the reed inlet valve.
I only wonder how effective this inertia can function, as the Ryger's transfer ducts are very short and anything but flow-encouraging.