And this notion matters for a surprising number of mechanics and/or cards: It's free real estate
In fact, he is one of several useful Stage 2 Water types, so he would be at home in a deck based around Archies that picked out the right Water Pokemon (Empoleon, Swampert, Blastoise) for the right situation
it does not remove effects already on a Pokmon
If the next spell you cast after Wand of the Worldsoul's ability resolves already has convoke, giving it convoke again doesn't have any real benefit
It can be quite surprising to learn that common cards from their childhood collections might be worth hardly anything at all, while certain cards can be worth hundreds
Obsidian Flames leaned into that, putting Charizard front and center as the headline ex for the set