You ought to give them a test, and see if they actually do know all of the rules and published spells in the game. Make them back up their claim with a knowledge check. ;)
In your original post, you suggested that PF2 might offer a player better opportunities via class feats. How would this be implemented within a 5e chassis?
Yeah, the 5e wizard definitely needs something more than spells to define it. Are there any really good Wizard brews out there to replace the official one?
Whereas in Pathfinder 1st Edition, you were given the choice of playing the base class or playing one of the many archetypes of the base class. So you could be a Fighter and work your way through the picking of general or combat feats to meet whatever concept you had in mind. Or you could pick...
Which is probably why the Barbarian class was renamed the Berserker class in Level Up. Monks, Paladins and Warlords were all renamed in this RPG (Adept, Herald and Marshall).
Sure, a new spell could just appear out of nothing, but is it a useful spell? And if one does appear, how do you go about catching it? That new spell isn't going to sit still for you to catch it after all. :p
If Laser Llama happily came out and told everyone they were collating all of their work into a single hardcopy book, how many of us here would buy said work? ;) I know, I would buy it. 😁
I would be fine with it because I have known my DM for almost 20 years, long before he invited me to join his role-playing group. There are going to be things that only the DM knows and has access to, and they have their own reasons for either withholding info or giving it on a need to know...
It's more fun if they don't know what they have or why nearly everyone in the entire multiverse seems to be after them. 😋 You could even have it where the item in question had a spell placed on it that makes it appear to be a very ordinary object.
"What have we, what have we, what have we done...