SOME LETTERS OR ALL LETTERS
Finder treats what you enter as a pool of available letters. A result may use the whole pool or only part of it. With APPLE, the English list includes APPLE as well as PALE, LEAP, PEAL, PLEA, PAL and LAP. This is different from an exact anagram search: Finder keeps useful shorter results instead of requiring every tile to be spent.
Letter frequency still matters. APPLE supplies one A, one L, one E and two Ps. A candidate can use no more than those amounts. PEPPER is therefore rejected: it needs three Ps, two Es and an R. Type a question mark for one blank letter; each question mark can cover one missing character.