Re: Or Not
There are certainly similar situations, but they all presume full language competency is already there.
But imagine if someone only ever answered when their name was called by echoing it. We'd think them deranged or deficient somehow, wouldn't we? Then imagine that everyone was like that. We just call out our names, and maybe, very occasionally, call out someone else's, and when we hear our own name we just repeat it. Then we'd be just like the dolphins. Nothing wrong with that. Quite useful, really. We could keep track of one another, the point being here that we'd recognize that names refer, to ourselves and some others. Mothers would be able to locate their offspring in distress, for example (baboon mothers can't do that, but we still think they're pretty smart).
Having a signature call for yourself, along with a small set of signal calls is one thing. Intentionally calling another to gain their attention or to summon them is quite another. When Tarzan gets from "Me Tarzan" to "You Jane" he's jumped into language, and then the medium is bound to expand: Who? Yes, No, and so on. I see no sign at all that dolphins have crossed that Tarzan threshold.