There's a big difference between Garcia being third choice CB and Foden potentially being 5th choice CM behind KDB, Bernardo, Gundogan and Aouar, pushing him to play in other positions like LW where he isnt as good.
I think even Garcia will consider himself deluded if he thinks he's going to take the mantle as a starting CB at 19 years old in one of the best squads in football. Even as a 4th choice he would get plenty of game time, if he enters next season as our 3rd choice he's laughing.
Foden has had Pep gushing over him for two seasons saying he's the heir to Silva. Going out and buying another player to play in his position when we already have multiple other options (and other academy talents ready to take up a back up role) would be so ridiculous after all the things Pep's said about him.