Once your league reaches the playoffs, waivers work a little differently. Since the standings no longer update, we use rolling waivers throughout the fantasy playoffs.
This means that once the standings update after the final week of your league's regular season, the waiver priority will use rolling waivers until a champion is crowned in your league.
Regardless of whether you have "Reverse Standings" or "Rolling Waivers" selected in your league settings as waiver type, they act as rolling in the fantasy playoffs.
Of course, your league and commissioner can edit the waiver priority as desired if you choose to go about it differently.