Of course they could, & may do for all I know, but does it not make perfect sense to you & indeed everyone else, that City would try to get the best price for players leaving, & should it really need highlighting all the time ? Can't people just use a bit of common sense ?
I'm pretty sure people have made this point before, as a possibility which may come up. Not just now, but in previous transfer windows. It can also work the other way, that the manager will not want to shed certain players unless either there is a strong likelihood of another coming in, or the offer is too good to refuse. I'm not sure Pellegrini will be happy to release Dzeko without a nailed on replacement player for instance, unless he's been told he has to, or unless the price gives us further bargaining power.
If we are serious about DeBruyne, I imagine the bidding process will now start or perhaps the actual transfer.