Yes we could buy without any sales but that would leave us in a terrible position when it comes to offloading players and is just awful business practice, we're the best run club on the planet, we're not going to be doing that, thats a glazer move. As you say, We're going to take a hit on those players as is, We're not going to put ourselves in an even worse bargaining position.
I only said we have to act as though we're keeping them, until they're gone, not that we are going to end the window with them in the squad. There's what, 5 weeks? of the window remaining, there's plenty of time yet, just look around, there's been practically no business done as of yet in the league aside from villa who are side stepping PSR problems, dippers haven't signed anybody, arsenals only signing is the obligation to turn Raya's loan into a permanent signing, spurs haven't signed anybody.
This is purely guesswork here and I may be proved wrong but I imagine they'll be no movement in or out whilst we are on tour. only after the tour ends and most of the squad are together will the futures of the peripheral players be sorted and then we will be in a position to do business.
It's not awful business practice - that would be putting yourself in a situation of neglecting a position of need, ostensibly for the sake of 2 players, who won't be part of the manager's plans, and to make minimal savings.
What other clubs are doing isn't relevant but even then you have missed Archie Gray (£40m) and Arsenal pretty much all but confirmed the signing of Califiori.