Even though Apple equips both the new iPad mini 6 and the iPhone 13 with its quick A15 CPU, differing clock frequencies lead to a small performance difference in the single-digit percentage range that should only be noticeable in synthetic benchmarks.
https://www.notebookcheck.net/Underclocked-The-A15-chip-in-Apple-s-new-iPad-mini-6-is-slower-than-in-the-iPhone-13.562249.0.html