Everyone is going to pitch the 7thg or 8th occasionally in a bullpen, especially when your Plan A guys are getting lit up. Your statement even if true is not particularly alarming.
He was a matchup lefty, so he pitched some matchups in high leverage situations. It was early in the year, and seeing if the guy could do it under live fire was something that needed to happen if he was going to be counted on later, heck every team experiments like that in April when the games aren't percieved to be quite as important.
It didn't work, he was released, end of story, to try to turn that into some mad conspiracy theory where Shoeneweiss was used regularly as a setup reliever is just... bizarre. It shows no connection to reality much less any understanding of how a season is played through at any level, much less the majors.