It's not what the engines burn, it's where they take you.
If your friend is like most 900 hr pilots, they don't have much experience operating pressurized aircraft in the middle altitudes dealing with icing and thunderstorms on a regular basis. They usually don;t have time operating into high-density terminal areas (some arrivals can get very busy, especially single pilot- look at the plate for the Civet arrival into LAX for example), and are not used to thinking ahead of an airplane that is going twice as fast as they are used to thinking, capable of taking them in excess of a thousand miles without refuelling, getting more weather, etc. I have taken a King Air 200 nonstop from TPA to Jackson Hole, Wyo . . . . obvioulsy, a pilot needs to be as capable as the aircaft they are flying.
A professional pilot, or a pilot with the attitude of a professional, will learn all these things over time, and your friend probably will too, but the insurance company will want him to have sim-based training and quite a bit more experience, probably at least 500 hrs in type, given his low time.