Nah, I'm just guessing they want a lefty in the mix occasionally with Yepez and Chappy (and Call). As between Blankenhorn and Gallo, Blankenhorn got his chance, so can't complain, so they are basically giving Gallo his chance to play himself into a better position. I'm sure they told him, "look, we'll give you a shot under these conditions, and if you can't live with that, then we can release you and you can see if there's anyone who would actually play you more." The team is low on veteran leadership at this point, besides Vargas, so there's that aspect too.
Per Zuck: Gallo will get some playing time against RHP but the priority, according to Davey, is to give playing time to Chaparro, Yepez and Tena.
What is the purpose of this? Bring him back next year and try to flip him at the ‘25 deadline?