And is it even reasonable to use it, since it has 600+ pages?
Not all functions are simulated in the sim’s G3000 (not all even could be), so that would cut the number of pages required. There’s also a Cockpit Reference Guide that’s somewhat shorter (272 pages), which you can try to look at if the Pilot’s Guide is too long
But yes, in what is functional you can very much use these manuals, and they will be near always accurate - to this date I think I found one extremely minor discrepancy in the 120h/65 flights (+10h on the very similar Longitude)
Short answer is yes. But the G3000 as we have it is severely crippled in many key areas and desperately needs to be revisited (along with the 530/430) by working title to add more functionality