There is always a clear difference between fun spin-off and a canon game.
Spin-offs as Freddy in Space series and Security Breach: Fury's Rage are very, VERY different and clearly made just for fun. They do not try to tie into the canon games.
Into the Pit not only has a clear storyline connected with already established places, characters and events, with many references to canon games which weren't mentioned in the original story. Examples: poster of Toy Bonnie (Toys appeared only in games so far, none of the novels), Helpy and members of Trash and the Gang in a dumpster (also didn't appear in novels), and even poster of Fredbear from Security Breach. I could go on and on. The description literally states it will help us to solve secrets spanning decades. Why would this be stated if the game was non-canon. If it were non-canon, then the answers to those secrets would dubious at best, and would be on the same level as The Silver Eyes trilogy.