Only by reputation, I've heard the same but don't have experience with it. Another highly decay resistant species is Eastern Redcedar. Remember the sapwood of all species is not decay resistant.
Film forming finishes perform pretty poorly on large timber from my experience. Checking is inevitable, bulk water gets into the checks but is vapor cannot readily get back out through a largely intact film. The moisture content of the entire timber rises to the point where it can support decay fungi and the film becomes a compost bag. Breatheable water replellant finishes seem to work better. Repeated coats of them can cause a film.
