Not authentic to what? The DRGW?
There were plenty of oil fired 2-8-2 locomotives in the US.
Neither are the passenger cars converted from flats, propane heaters in the cars, holding tanks for the toilets, water sprinklers on the stacks, pristine ballasted track, radios, computerized ticketing, modern machines in the machine shop and many other things that have evolved since the sale by DRGW.
I really don't care what boils the water to make steam....as long as it makes steam, because that is what powers everything....it is still a steam locomotive.
My 2 cents.....