My thought process could be way off track here, But I'd imagine that BMW really put these engines through the paces while testing. Wouldn't surprise me if these engines idled for hours if not days during testing. How could they sell bikes if the engine would cook itself after a short time. Would I sit my bike out to idle for an hour or so, absolutely not. 10 minutes would be too long. But there are areas where massive traffic jams are normal. I lived in Houston for 11 yrs & down there the sun sure does shine. I did ride an old '74 Yamadog 750 down there & it never fried.
I know these engines are decades old now & certainly not as durable as when new taking that kind of abuse.