Many cards printed before the Core Set 2021 release have received errata to instruct a player to mill cards rather than to put the top cards of their library into their graveyard. Use the Oracle™ card reference at Gatherer.Wizards.com to determine whether a specific card has received such errata. As a rule of thumb, if an effect instructs a player to look at or reveal a card before it’s put into its owner’s graveyard, it’s unlikely to have received errata.