If the player has a few empty shelves, then customers have a smaller chance of purchasing something
In GLC you play a 60-card deck, but you can only use one type of Pokmon (Fire, Water, Grass, etc.), you can only use one copy of each uniquely-named card (for example, you can only use one Pikachu card, not multiple copies of different Pikachu cards), and all rule box Pokmon like V/GX/EX, etc
There isn't much talk in any of the competitive formats about a serious use of Tezzeret, Betrayer of Flesh, and you will only see a few casual commander lists pop up here and there
Pokemon TCG Pocket Lapras ex deck The best Lapras ex deck in Pokemon TCG Pocket uses just four Pokemon cards
Ishihara in particular was fond of card games and used that insight to advise on how to add more depth to the battle system