Musil is a bottom six player, and that's where they used him in limited minutes. Musil, to his credit, performed well. Thompson, IIRC, also played in their bottom six at the beginning, and he joined them much earlier in the season than Kyrou did. He also broke into the NHL in a bottom six role. Walman started off with bottom pairing minutes as well, IIRC.
Kyrou is a top six player, and would clearly be ineffective in a bottom six role.
If you think there was any chance that Chicago was going to throw Kyrou into their top 6 at the end of the season and roll with him, I honestly don't know what to say. That's not how Chicago operates. They sign AHL vets for those important roles, and they operate to win. There was zero chance that Kyrou was going to come in at the last minute and displace an established player like Bennett or Hyka who was already putting up a point per game for the team in that role.
If you think Kyrou not being a fit for a bottom six role is a red flag, that's fine, but I don't share that opinion. We can save the "red flag" stuff for next year when Kyrou will actually have a legitimate shot to carve out a role for himself.
I honestly can't believe we're talking about red flags for Kyrou at the end of a season where he was named player of the year for his league, and he led team Canada in scoring at the WJC. If anything, this was a wildly encouraging year for Kyrou, not a cautionary one.