I can't see anyway the Twins can get away with Option B if he's healthy. No minor league games for him to play in, MLB rosters have expanded, but you're just going to send him home?
What defense would they have against a claim that it's blatant service time manipulation? There should absolutely be a grievance filed if that happens. Now would/should the Twins care about that? I don't know, those take years to resolve, so in reality maybe it doesn't matter much. Still, it'd be a bad look.
I'm sure the Twins would love it if Buxton just suffered another injury that was bad enough to shut him down for the year, but not serious to the point where it would threaten his 2019 season.
Watch your back out there, Byron ...
I admit I don't know the answer with 100% certainty but I'm fairly baseball attentive and I don't recall a ton of reports of clubs getting nailed by grievances filed by the MLBPA.
Frankly, the CBA not only allows service time manipulation, it basically encourages it.
The Cubs manipulated service time with Kris Bryant
The Astros manipulated service time with George Springer
The Braves manipulated service time with Ronald Acuna
The Yankees manipulated service time with Greyber Torres
The list is waaaaaayyyyyy longer than this... "the bad look" is worn by every major league club and it doesn't appear as if the bad look has cost the Cubs or Astros or Yankeees in terms of acquiring players.