What Iscah and Mikko said.

Though this makes me remember Lahabrea talking to us using Ancient language in Thousand Maw of To-to Rak and then being delighted that we understood him.

I'd also venture to say that the researchers in Elpis are used to communicating via The Echo with their creations, their creations being animals, so a perceived familiar speaking an odd language probably isn't so weird to them in either case.