This is mostly relevant in post-sideboard games, where if you start dredging you will not be able to find most of your sideboard cards, but can also be relevant in Game 1 when you need to draw a mana source and/or dont have green mana yet
After some corrections, the more heavily distributed "Beta" set featured 302 different cards with a 7.3 million card print run
Similarly, adventure cards like Brazen Borrower and Bonecrusher Giant only count the main card for their mana value
Equip Artifact - Equipment Black Mage's Rod Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.) Equipped creature gets +1/+0, has "Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent," and is a Wizard in addition to its other types
This shows up in the story and via the new factions, but also in the art