Woo, I’m awesome!
I feel like what’s being described here is maybe ideal, 21st-century trad play. If “plot is what happens if the players do nothing”*, and so the GM has a “plot” in mind awaiting interference from the players, and players have agency, and their characters exist in a setting that a) responds to them and 2) has “secrets” waiting to be found that were placed there by the GM, then you have… a functional campaign?
I guess it’s less the emergent play that games like PbtA or BW produce (though those games certainly have prep), but rather everyone — GM and players included — prepping a bunch of stuff they can’t wait to show each other (the GM’s setting bits and NPCs, the players’ conceptions of and hopes for their characters) and then revealing all of that stuff over time, sort of like playing a hand of poker. Eventually all the cards will be on the table, but there will be a lot of back-and-forth first, i.e., the meat of play.
* I think maybe Dave Noonan or Chris Perkins said this about ten or more years ago.