It probably could be an error, but (a) they were coming home no matter what even though Semien looked like he would score no matter what, and (b) where they were positioned, they would have certainly been in a position to get Benge at first.
So while it's not the textbook fielder's choice, I'm not sure what would have been the more accurate scoring. It wasn't a hit. I guess it could be ruled an error on Schumann, but he he wasn't getting Semien, and it's not his fault that Volpe or Chisholm or whoever ran into him.
I mean, he was trying to come home, and just got his senses knocked out of him by a full-on body check.