Good point. Xenobiology is unexplored in toki pona.
For example, is Spock soweli or jan? Vulcans seem to be able to interbreed with humans.
Jabba the Hut is clearly akesi.
Just about everyone in Star Gate is jan, even if they appear to be a different species or from a different galaxy.
The message, imho, is trying to make a distinction. We're people (you aren't). We're from earth (you aren't).
So if jan is all 2 legged creatures, and they are Vulcans, then we aren't making a very clear distinction-- as if we said "We're living beings"
Same thing goes for naming our planet. If we don't have a word that contrasts with what the aliens live on, then we'd get the vacuous observation "Hey alien, we are living beings from, some planet somewhere"
They will receive our radio transmission and be all so excited and then when they translate it they say, "They guys are boring-- nothing to say."