Simon summed up what's going on just fine. Obr is full of bull. Yes their engines run fine, but don't make 9hp from 30cc. At least not with a loop scavenged engine.
Ive run plenty of big engines on dynos to know none of them are exact to another one. Heck the same engine on the same dyno on different days give a + or - 2%, and I've seen eddy current brakes give different readings then a water brake. Dosnt matter so long as it's consistent and all work done was on the same dyno. We beet this topic to death with the saws too, other then they are all really close to rated output, because there are governing bodies that force them to be, just like nearly every other engine mfg out there. They legally have to be within a certain % of output. Oilimat, obr and whomever else are aftermarket guys, no standards to adhear to (no offense) so it's not like they have to live up to the numbers they say. If they deliver an engine that runs well the customer doesn't care what the dyno sheet says.