Maybe there is a deal, maybe there isn't. None of us are privy to that.
However, if there IS a deal, I highly doubt any GM would back out after it's agreed upon, just because something better came along. It's not about being afraid of hurting feelings, or anything like that ... it's because while they're all competitors, they're also business associates. Almost every GM will at some point be fired, and probably have to take a gig somewhere else as an assistant or with a scouting dept. And if you've built a rep as someone whose word means nothing and who's in it for himself, you're unlikely to be hired by any other team president or GM to work under him, because you're already proven to be untrustworthy. If you'll burn another team's GM for an okay player, you'd probably burn your boss for his job too.
While Manson and Vatanen are good players ... are either of them SO good that you'd burn your reputation over them? If I were a GM, I wouldn't. I might do it for a franchise or near-franchise player, but such a scenario would likely never come up, and even if it did I'd have to accept that it might be the last team I work for.
Contrary to what many believe, the most successful people in business aren't the ones who backstab people they work with. The best executive in sports over the last few decades is probably Jerry West, and I don't think any other GM has ever questioned his credibility or integrity.