This is just a paraphrasing of the old WC3 description.
From the manual:
Though murlocs are relatively new to the Eastern Kingdoms, it is increasingly believed that they are actually a very ancient race of Azeroth. These creatures have been moving in-land steadily from their oceanic dwelling places and inhabiting more areas of Lordaeron.
People need to chill. Not everything is a clue. Some copy guy in marketing would have been told to describe Murlocs based on existing material.