Section links in head words
No, it isn't, but my point is that the etymology is to be found at the entries for the component words. Do we ever give etymologies for phrases when the etys are just the etys of the components? Certainly things like bee's knees and cat's pajamas give etymologies, but of the history of the phrase, not its components. Etys for cat, bee, pajamas or knee cannot be found at those entries.
This is why {{compound}} and similar templates have a gloss parameter; besides being just for clarity, it's to specify which of the senses the term should be understood as derived from. Similarly, if "cat" has several senses, then just linking to cat is not a proper etymology because it's not clear which of the senses the phrase derives from. An etymology section should be added to clarify this.