My reasoning was that this was more or less hackery and I wanted to abstract the implementation of how it knows. I could have added an `is_sort_only` property to `DetailColumn`, but it seemed silly to interfere with the actual model; could have added a dynamic property `_is_sort_only` inside `create_temp_sort_column` but that seemed to arbitrary and poorly documented. But either of those would have worked and I could have used this function to do either of them. I basically didn't want to affect the actual model at all, and not have any other part of the code have to care about how I was flagging the mock-columns.