I don't agree for a bunch of reasons, but primary among them is that it's good to be honest. If you don't plan on selling integral players in the summer, tell guys that when they come in so they get less upset if and when a summer move is rejected.
I'm not saying this is the case, but if Long has an expectation that he'll be sold in the event of Euro interest, regardless of the window, and he doesn't get sold this summer, he's going to be a miserable bastard for the rest of the season. That's not good for anyone.
Telling prospective signings that you're open to winter sales is better than most teams in MLS anyway, so I don't think it would have much of an effect, if any, on player recruitment.
Totally fair. Im not arguing that they shouldnt be honest and transparent. I, of course, want them to conduct their business with players ethically and in good faith. However, fundamentally I think they should be open to transfers in both the summer and winter for many reasons, the optic to potential acquisitions being one of them. Hence, they need not have any sort of policy regarding seasonal transfers.