Are you referring to the Browse page that shows content based for just Sunday? I think this all depends on what listening region one is in on the Spotify service, but I get both Xian offerings as well as secular offerings of curated Spotify playlists, like the Gameday curated Spotify playlist that is highlighted for Sundays.
Can you provide screen shots of the rack of Happy Sunday! that you are seeing with the Spotify app? You might have to do more than one screen shot from the app you are using, as the rack has arrow page controls left and right on the desktop app, and scrolling right and left for mobile apps.
Just want to add that I get this too. I listen 75% electronic/club/house, 24% pop, 1% other (but NOT christian music). Yet, Spotify keeps recommending Christian music to me on my home page. Christian music has a whole rack on my home page, along with "you might also like". Can we just completely block a whole genre or something?