Knowing how much mana green generates these days, an overwhelming amount of squirrels is easy to pull off
Here, we are told that these cards are being banned because they either allow for "unhealthy play patterns" or "restrict viable deck-building options"
Keep in mind that before a lock has been established (with either no opposing creatures, or tapped down opposing creatures), it is likely that as the Stasis player, you have taken considerable damage
Additionally, its easier to play a Tarmogoyf than a Murktide Regent, especially if your opponent is bouncing your permanents with Teferi, Time Raveler
This just adds up so fast, just think of your favorite token maker and turn that non combat damage way up, and the best part, if you're locked out of combat, this can still win you the game
So using a card from your hand as a resource is clearly not a new mechanic