Yeah, I mean it seems to me like this situation is a bit blown out of proportion. The Sox left Sosa unprotected last offseason; if there was Rule 5 draft, anyone could have had him. Obviously he's blown up this season and become a much better prospect, but he would have had to have been added to 40 man this coming December anyway. Calling him up and not playing him is/was stupid, but he ended up playing in 4/5 games he was here and looked mostly overmatched.
If the plan was indeed just a short term plug until Moncada's return, they probably should have just grabbed someone off the waiver wire they were willing to DFA in a few days. Most of Sosa's PT was because Harrison got hurt AFTER Sosa got called up; so it seems like they either didn't intend to play him much; or TLR and the FO disagreed. But is it really worth getting your panties in a bunch? Sox gave the kid some reps and let him taste the big leagues. It was a tiny sample, but he didn't do much. He is the right person to get demoted - accepting that Leury isn't going anywhere - based on the current roster.
It is bad process. But its really not that big of a deal. If Sosa cannot become a major league quality player by 2025 when he's out of options, he's probably not really worth getting too worked up about anyway.