My guess? options. If Yolmer is out of options they could lose him. Mendick obviously has at least one option left because they just used it. This way they keep both instead of maybe one of them.
Two weeks of reliving the Tatis/Shields deal in addition to how often that happens here anyway sounds more miserable than dealing with Cubs fans in a Cross Town series.
For his hitting style, when Eloy is right, he is hitting like Magglio. Use right and right center, and hit the ball out of the deepest parts of the park. He gets into funks when he gets pull happy.