The idea is that anyone who puts ranks in spots almost always puts them in listen as well, and it's a bit of an oddity for someone to be eagled eyed but not have at least somewhat keen ears. Same for a lot of the other combos, like hide & move silently. The idea is to make skills easier to deal with so that you don't have to look down a list of over 30 skills. I can see some issues with climbing, jumping and swimming being together. And putting search with spot & listen. I dunno what to do about that. Maybe it's a tradeoff, maybe it's an idea killer.