Yes, they can get massive if you have enough life, but just being a big creature doesnt always win you the game, and they dont grow as the game progresses, only when you have 50 or more life
Each turn, you can cycle a card, get a free spell from your deck thanks to Unpredictable Cyclone, use Astral Drift to flicker Eternal Witness, and then, when Eternal Witness comes back into play at the end of the turn, you can get the cycler back from the graveyard so you can cycle it again during your opponent's turn to get another free Unpredictable Cyclone card
The card advantage on it is so mediocre that it ranks cleanly below Sword of Hearth and Home on tier lists
Creatures are more of a tool in the Dimir gameplan than a surefire route to victory
I have no idea if they are making more cards than these or if the really insidious fakes are coming from another source entirely