That kind of goes without saying, doesn't it? The two ('true route' and canon) are somewhat synonymous, at least in my mind.
For me, the importance of how canonical something is only extends as far as how extensive the body of work for a series is. For something like Star Wars, which has a large extended universe, it's a pretty important designation when it comes to discussing things like character and world events. For most VNs - for example Deardrops, which only has a small continuation in story in the form of a fandisc, it's only important so far as discussing the sequel.
For VNs that don't have fandiscs, proper sequels, or adaptations, what's canon is completely worthless.