The tag info for the aliens tag states:
For questions about a different and uncharacteristic species or object that has come to the world from another world. NOT for questions about extraterrestrials in their native environment.
This excerpt (particularly the second sentence) does not seem to align with the current usage of the tag, and to me personally, does not make much sense. In its current iteration, there does not seem to be a tag for questions dealing with extra-terrestrials in their native environment, as the only two relevant tags are aliens and xenobiology, both of which currently specifically exclude such questions.
A better excerpt in my opinion would simply be something like "For questions dealing with extra-terrestrial life".