These cards shine around the entire border of the Pokemon art, and they make opening a pack without a rare card feel less bad
A three drop with a nicely defensive statline, Cosmogrand Zenith has a ton of flexibility
When you would deal noncombat damage to a foe, you can exile that many cards from your library and play them this turn, so this is card flow since you can cast a few spells and drop a land each turn
Yes, TAG-graded cards are increasingly accepted in the marketplace
With other complementary artifact mana sources like Thran Dynamo and Grim Monolith, decks could count on being able to get the kind of mana you'd need to justify packing the cards that would let you use the mana from Metalworker to deliver the knockout blow, and their presence lets you turn that Metalworker mana into permanent giant amounts of mana rather than just a one shot deal
So, there you have it the fascinating journey that takes a Pokmon card from concept to reality, all within the confines of a 2.5x3.5-inch canvas