Bumbleflowers not the only recent example
Magic: The Gathering Assassin's Creed also includes an additional 2 mythic rares, 6 rares, 8 uncommons, and 9 commons exclusively found in the Starter Kit
Essentially, these are two philosophies that keeps common cards simpler on the whole, allowing for lapsed players and new players to more easily enter the game and quickly understand basic concepts and cards, while allowing for more complex cards and mechanics to exist at higher rarities
But what really kicks it over the top is that middle part of his text box: Whenever an opponent casts a spell, if no mana was spent to cast it, counter that spell. You dont have to worry about an opponent casting a Force of Will while tapped out, or a free Fierce Guardianship or Deadly Rollick
You could even reliably run Varina, Lich Queen as your Commander to maximize card draw and graveyard shenanigans
The deck has a lot of ways to produce ample mana for this very purpose