Not a saltie...but coral spreading means that they grow on all different sorts of places depending on lighting and flow, and some grow more faster and vigirously than others I guess, classifying them as semi-agressive or agressive. I wouldn't think all corals are like this but I'm sure there are some out there that are. Again, not a saltie, this is all from research.
"If you're not making mistakes, then you're not doing anything. I'm positive that a doer makes mistakes."