I'm continually surprised at how worked up people get about the 30th spot on the roster (depth-wise).
To me, Keirsey, Helman, Castillo, Carmago, etc, are all essentially the same AAAA player.
Same with Martin and Lee, except with the "prospect" label.
Yes some are better on offense or defense or are faster or bat LH vs RH, but that's why options exist. The Twins will move all of these players between Saint Paul and MLB as it fits their needs. A demote, just like a promotion, is never permanent. Heck, half this thread is trying to figure out this week's 5 roster moves. It's always changing.
But I appreciate the passion y'all bring about it for sure. In summary, I don't think any of these fringe players are difference makers anyway in terms of a 162 game W/L record. They all deliver about the same value. Keeping Kiersey up for now tells me this is "playoff mode" where defense matters (more).