This is not a sneaky attempt to inflict Catholic propaganda on anyone. Sayers was Church of England. It's an attempt to provide a source with as good an introduction to the whole way of thinking as one is likely to encounter.
And if I hook even one person into reading the entire Commedia I have done a good thing. Lewis (also Church of England) thought it the greatest poem ever written. So do I.
There is a huge danger in reading secular opinions of scriptural teachings. I dont even read Lewis for that reason.