Reading the study (the actual paper, not the linked article), it seems expected and sensible.
A conjecture is that aquatic adaptation is not reversible because there are already animals on land that can out-compete animals attempting to adapt back onto land (similar to how there have been very few transitions from aquatic to land in the first place).
Of course, in actuality this does not mean the transition from aquatic to terrestial is not reproducible, just that it would require a removal of the prohibiting factor such as a mass extinction event killing off most or all life on land.