Yes, the DOHC is well known for beating up the roller drive in those clutches. And they don't take well to the modern oils with the 'friction modifiers' that replace the zinc which is pretty much gone out of oil now. So a LOT of better quality oils can make the starter clutches slip. Using bike specific oil can help if it is one that is JASO rated, it will still have zinc but be prepared to pay big for it as now those oils are for 'specialty use' now and the cost has gone WAY up. The zinc dithiophosphate additive is now out of favor due to the phosphate component, the EPA ruled that oil companies nix it.
It's not that the oil is synthetic by and of itself, it's the other additives used now along with being synthetic.