Why yes it kinda is. they scrapped and reworked alot of systems. it uses a success system now and it plays quite well. so far i have not had to bend a single rule at all.
Yeah, I've purposefully run games "by the book" over the years as well as playing home variants.
The World of Darkness games (new and old) come to mind first, but I've also played every edition of D&D (except 2e, never played that at all) at one point or another "by the book".
I also played the majority of the old TSR games by the book as well as many of their contemporaries - Star Frontiers, Top Secret, Teenage Mutant Ninja Turtles, Robotech, Boot Hill...
I mostly try to do it "first time" with a game....but some times that only last the first section. White wolf tends to do well that way....I'm a BIG fan of the old Deadlands system but I have tweeked it a few times. I think its the nature of use game maker types....... we just aren't the one who go "THESE ARE WRITTEN IN STONE!!!!" ...more likely to look at some thing and say" I got a great idea....if I do this this and this......"