why did 尻尾 just break my spreadsheet categorization

I'm at Hour 842 (Phase 2.4 Anki) and just hit 尻尾. I already categorized 尻 under anatomy (Sub-deck B) and 尾 under biology (Sub-deck F). Having them combine into one word completely breaks my database schema. Why is 尻 (butt) even in a tail word when 尾 already means tail? This adds an extra 1.5 seconds per review. My daily efficiency is down 4%.