It wasn't over 6 games. It was what they've seen over years of watching Swihart through the system, including his time with the big club last year, in ST'ing and those 6 games.
If this is the case, and they've felt for a while that Swihart wouldn't/shouldn't be catching long-term (if that's what you're saying), then it would have been wise to trade him when his value was stratospheric. He could have been a primary piece in a trade for a starting pitcher last winter, and Hanigan/Leon could have managed behind the plate for a month or two until Vazquez was ready...but instead they put Swihart out there for a handful of games, demoted him, and converted him into a left fielder of questionable offensive value, where he promptly got hurt running into a wall. Maybe the team's opinion of Swihart wasn't changed by 6 games, but this smacks of poor planning nonetheless.
Preaching to the choir. I've been suggesting trade packages led by Swihart, not because I don't value him, but because his value to us as a LF'er (3B/1b whatever) and eventual part-time/back-up catcher is less than his value to another team willing to look beyond his current defensive shortcomings as a catcher and plug him right in there (once he's off the DL).
If you look aat the state of catching in MLB today, not only do some good teams have weak defensive catchers, they also lack in ofense. At least Swihart should give them one part now with hopes the defensive part comes along quickly.
Almsot all my winter trade suggestions involved some combination of Swihart, Devers, Margot, Guerra, Owens and Johnson for an ace or possible soon to be ace. (Note: that was before some of these guys saw their stock decline a bit.)