I think with at least a few folks, there is a misconception that the crossover point is like a brick wall and beyond that we won't hear anything with enough SPL to matter. Without listing a crossover slope, the crossover point has limited meaning.
Another thought, let's say just beyond the -12 db point is a peak due to the room. If you have your sub running hot, this can make for significant output beyond the crossover point.
I realize not everyone has REW but an actual graph really shows what is truly going on with one's sub.