Unfortunately, thats not really a claim anyone can verify. The simple fact is a games length isnt based on its word count.
Being someone that has worked it game marketing in the past, I can give you abit of insight.
Basically, if a game is marketed as being 100 hours long, its generally an estimate based on the average of the play testers.
Personally, I've not really had much experience when it comes to visual novels so I cant say to much, but my understanding is that the length is generally based around one of two things. Average based on the play testers or average reading speeds. I dont know however if in either case the average is based on a single route or something like that, but I would assume so given how ridiculous the numbers could get otherwise.
I will say, it does put the game up there among some of the longest books ever written though. Granted, I havent been through alot of the game so I cant say how linear the game is.