In a comment to a recent question, @Nosajimiki made a good point. The OP had not tagged the question hard-science or science-based, so I chastised other respondents for taking a hard-line Real World stance about the OP's premise based on the idea that Real Life cannot be an overriding limitation on any question unless specifically requested.
@Nosajimiki pointed out that the xenobiology tag demands hard science.
At this time "xenobiology" is strictly defined using the Wikipedia page, which is discussing (and these are my words) the professional study of biology in terms of what chemistry could allow outside of Earth-centric biology. In other words, the Wikipedia page isn't discussing creature-design. Far from it.
In fact, the fundamental problem is (since new users never read tag wikis) that users are using the xenobiology tag based on their own personal expectations and not at all based on what wikipedia says about the academic investigation into the limits of chemistry-based biology.
"No" would mean rewriting the Xenobiology tag wiki. Frankly, it's a poor wiki right now, relying on another web page which can change and has, itself, nothing to do with worldbuilding to establish the context of the idea for worldbuilding. Honestly, I think the wiki should be improved regardless what decision is made here.
Existing tag short-summary
Use this tag to mark questions related to creating plausible alien biologies that may be close to or far removed from Earthly biology but within the realms of hard science.
Existing tag wiki
See Wikipedia entry. Xenobiology describes a form of biology that is not familiar to science and is not found in Earthly life. Novel biological systems and biochemistries that differ from the canonical DNA-RNA-20 amino acid system, which can include variations on the same these (e.g. different amino acids), totally different systems (such as the SF staple of silicon-based life).
This can include different biochemistry, or different biological systems and organs without regard to the underlying chemestry.