I think it's likely that if we were to see them as "alien" they would need to be the same or very very similar to human form. Otherwise, it's likely we'd just call them a beast of some sort. Would you say a Gorilla is alien to a Human? They're not that different. Would you say a Dolphin and a Human are too different? They both have the capacity for independent thought, a consciousness, and are self-aware.
It would make sense that if you're going to make first contact.... you want to meet those folks on the most similar or relatable terms.
Humans read body language a lot and such. It would probabbly facilitate a lot of communication to emulate human behaviors and etc to get started. Reduce tensions, communicate better, etc.
