I'm guessing it is in fact a Sturmey with different ratio gears and Brompton's marketing is overstating their effort.
I'd guess Brompton's marketing is accurate. SA's designer of the 8sp hub went to Brompton when SA folded. It wouldn't surprise me if he designed the wide range hub and then asked Sunrace-SA to build it.
A post on the Brompton Yahoo list notes the number of teeth on the epicyclic components. The ring gear has the same number of teeth as the current 3sp.