It has nothing to do with the show proper. Basically, Bandai have gone out of their way to muddle the waters regarding the main couple's relationship, refusing to let it be explicitly referred to as "marriage", etc. What makes different from other queerbaity cases is that the show itself wasn't actually ambiguous. They never said the word "marriage" directly, but the couple were engaged for the whole show and in the epilogue they were wearing wedding rings. The attempt making ambiguous something that very clearly was not infuriated a lot of people.