Shardstone
Hero
I'm not considering 500 spells. You have deliberately twisted what I said into something else.Because it's easier to consider 25 spells than 500 when working up his tactics? And because a listing of spells is an easy way for the designers to add a little depth and flavor to the character, rather than saying "You can give him whatever spells you want."
I mean, you can always discard what's listed in the stat block and replace it with something that better suits your needs. That's true of every monster book. I'm not tracking how that's more or less a feature of this new format.
I came up with Disintegrate, Wall of Light, and whatever else I said off the top of my head. Because those are cool spells I already know about. I wouldn't think much harder then that. And with DND Beyond, I can filter by level, source, and school.