Yes the Northern atolls focus on deep thilas, not sharks. I personnally found the North the most pristine diving in the whole Maldives, simply because almost no LOB go there, and very few land based divers.We've done the north several times which was amazing ~15 years ago, but most of the sharks are now gone. The central atolls are okay, but not nearly a pristine as the south.
Now if shark are your thing, then the Vilingili channel is a prime spot. But there are sure dive sites in Central for sharks too.