I don't think WWE care who goes to AEW and to be honest I don't think they have to.
I think they've realised that WWE as a brand will sell out shows all over the world no matter who's on the card.
Very few people have or will move one way or the other between AEW and WWE and be a significant "needle mover".
Look at the star power of TNA in it's peak, they never even came close to laying a glove on WWE - yet they're still the closest to having done so in nearly 3 decades now.
Realistically even if Roman, Brock, Orton, or all 3 at once went to AEW, it wouldn't make any significant difference to either company's numbers, other than wage bills.
So if they have the choice of paying a Will Ospreay big money to "jump ship" or just sign some random guy and put them into NXT and see how they do, they'll do that.