Well - the "beginner sharks" are usually called that because they are generally the best species for "beginners" to the shark aquarist world. It doesn't mean that they are good beginner saltwater fishes.
In fact I would highly suggest that an aquarist who's new to keeping saltwater fishes shouldn't even attempt to keep even a "beginner" sharks. Until they've got a couple of years experience with easier to keep predatory saltwater such as Groupers, Eels, or Lionfish. The reason is because - you can learn alot about basic shark keeping from keeping these other predatory fishes. Generally keeping sharks is consider to be more extreme than keeping these other predatory fishes - because sharks tend to tougher keep.
Still for a very knowledgeable & experienced marine aquarist - beginner sharks can be very easy to successful keep, And in some cases they can actually breed sharks.