I am fairly certain the engines are Triumph designed and built
But would need to do some digging to confirm
On the subject of dino oil in a motorbike, haven't done that since my XBR500 back in '92.
My Yamaha X Max had a tiny sump capacity and I changed it out early due to there only being a hard to access screen filter, I ran it on Castrol oil which was I believe a semi synth.
There is an over lander bloke that goes from NA to the bottom of SA on tours in a Super Tenere I think, he ran it way in excess of the recommended interval on that journey several times and when the engine was stripped in a motorbike magazine the engine was almost as new, think he did something silly like 70/80k on it with something like 4 or 5 oil changes
Will do some digging and see if I can get more accurate details or indeed remember his name!
He was the bloke that used to go round the world all the time on Yamaha R1's