On the surface the play is only a plus 1, but it sets up for extremely easy plusses in the future in the form of simplification of your opponents game state through steeds, additional monster from Ambush and 2 to 3 more searches use Ulti-Cannahawk on your next turn
You Can't Control What You Mill There can be very specific times where taking cards out of your opponent's library crumbles their strategy
And maybe you can make it work in a really creature-heavy strategy that wants to blow up a one-drop permanent for each opponent and then maybe hit two or three more the next time around
Players will leverage Strefans ability to generate Blood tokens and use them to deploy vampires that can drain opponents life totals
Spell/Trap Card removal cards are essential for combating these kinds of threats
There are many scenarios where a creature enchanted by Pretenders Claim will either A) be blocked and have the tapping lands ability not matter, B) just be outright killed, or C) connect because the opponent wasnt going to block anyhow