Flyers probably didn't know if Fedotov was coming over until it was a done deal, it's not like you can count on anyone leaving Russia these days, and he was a very delicate situation b/c of the politics.
But I doubt they promised Kolosov a NHL job, I'm sure they seem him as 2-3 years from the NHL. It's not like he's an elite KHL goalie who is a high probability to immediately succeed in the NHL. He performed very well for his age, which makes him a solid prospect, but KHL is still a "minor league" (and probably closer to AHL these days) and Kolosov did not dominate. Heck he hardly outplayed his backups.
What they probably told him was they expected him to be the starter for LHV (but he'd have to perform to keep his job, same as the KHL) and if he played well would be the first call up in case of injury. With Fedotov on a 2 year deal and Ersson unproven, there was a pathway to the NHL if he earned it.
What does he earn playing for Minsk? Obviously if the money is similar, he's prefer to play in his hometown where he's a "local hero." And if he burns off his ELC, can negotiate for real money in his RFA years.