Do you watch Teen Wolf? I imagine it's pretty common there, with people being invested in Sterek in fic, and Scott/Allison in canon (not that those are actually in conflict, but the main het pairing on the show and the main slash pairing in fic are totally unrelated to each other.)

I have to admit, I only realized recently (maybe with Teen Wolf) that there are people who do this, ie, enjoy the pairings that produce good fic fairly independently from how they consume canon.