The ones included here are an Amber/Emerald deck and an Amethyst/Ruby deck
Firstly, Tez is card advantage
With Modern Horizons 2 and, more specifically, Garth One-Eye, the community has found that we can still play with some of their effects, even if its not in their original form
For example, if you scry 2 and put two lands on the bottom of your library that you had absolutely no use for, people will often describe this as drawing two cards. Of course, you didn't actually put any material in your hand, so you didn't actually draw anything, hence the virtual card advantage
A 3/4 flier for four mana that mills 3 cards on attack feels more like a draft card than the face of a Commander product, even if you do get to keep an artifact creature or vehicle from among those cards