Xfinity on-demand shows missing on Tivo's

So after 7 days of fighting with Comcast I finally got my cable cards paired correctly and can get channels... What a pain in the rear!!! So now I notice not all shows that I see on their "X1 on-demand" show up on the Tivo version. Example: Rookie Blue shows up on X1 on-demand" but not on Tivo version. Just curious if that's how it works or how we know what shows will and won't show on the tivo version.