I think you're exactly right. Because originally the rooms would be the same as POP. But only the 2 (i think it was only 2) buildings were built back in early 200/2001. So those will be the regular Little Mermaid rooms. All the new buildings that they built do have the internal hallways and those are the ones with the suites.
I just saw this information:
Walt Disney World has announced an opening date for their newest accommodations, the Art of Animation Resort. The value resort will open in stages, with the first phase, the "Finding Nemo" section, opening May 31, 2012. After that will come "Cars" in late July, "The Lion King" in late September, and "The Little Mermaid" in late 2012. The resort is near the Pop Century Resort, and will boast 1,120 family suites and 864 guest rooms. According to the Disney Parks Blog, the "Finding Nemo" section at the Art of Animation Resort will house the largest swimming pool of any Disney resort. This pool will measure a whopping 11,859 square feet. A children's water play area and two other pools will round out the rest of the resort's aquatic offerings.