Historical Rules · 25 September 2020
Rule 701.20b
Official source text from the 25 September 2020 Rules release
Some effects cause a player to search a library for a card or cards, shuffle that library, then put the found card or cards in a certain position in that library. Even though the found card or cards never leave that library, they aren’t included in the shuffle. Rather, all the cards in that library except those are shuffled. Abilities that trigger when a library is shuffled will still trigger. See also rule 401, “Library.”