I recalled that Grichuk's numbers for the season were largely propped up by a hot start to the season, where he produced a respectable 113 WRC+, which was followed by an extended stretch of futility. I decided to do a different comparison between the two, comparing their numbers over the last 4 months of the season after Grichuk had cooled off. It turned out that Grichuk was actually less valuable than JBJ during this stretch of games.
From June until the end of the season in 252 plate appearances JBJ produced a 39 WRC+ but only was worth -0.3 WAR as he provided value defensively and on the bases. Comparatively in 337 plate appearances Grichuk produced a 66 WRC+ and was worth -0.5 WAR. A trade of these two players if this performances were to continue would have potentially been a pretty even deal for both sides, but Milwaukee would have been ending up with an extra year of a terrible player vs the single year that they would have been stuck with otherwise.