Just spent far to long Googling this myself.
At least size wise and passenger wise the Dolphin seems to be a better fit for the "Yacht" designation. Based on it's size it would even fit into the "Superyacht" class along with the Orca:
Cabin cruiser:
-7.6 to 13.7 m (25 to 45 ft)
-Can be usually operated by the owner
Yacht:
-Normally 7 to 24m (23 to 79 ft)
-Usually requires a professional crew
Superyacht:
-24m to more than 180m (79 to 590 ft)
-Like a Yacht requires a professional crew, though more roles (captain, chef, interior staff, deck drew, engineers)
-Mostly restricted to 12 passengers when used commercially (excluding crew)
Cruise ships/Ocean Liners:
-70 to 361m+ (230 to 1184 ft+)
-Stricter safety standards to have beyond 12 passengers (eg large lifeboats in an emergency)
-Commercially owned
Liners were the ships that took passengers to other countries before passenger aircraft took over that role, so they aren't many working in that capacity as there is a bigger market for luxury cruise ships to focus on making the journey experience itself the highlight rather than A-B travel.
Relatively speaking, it probably makes sense that the Dolphin would be classified as a Cabin cruiser/Yacht; but this is pretty much my subjective opinion bought about by a bit of Googling
