Shadow Gens directly mentions story-related things from Sonic Channel, which is mainly accessible to Nips. Still gets directly referenced.
IDW can exist for 7~8 years and not get a single mention anywhere in the games.
>Tangle is mentioned
Yeah, in easily missable dialogue in a 20-30 hour game. The Conductor and his fat wife are shown in IDW, and the visual novel they are from still isn't canon.