These comments are fecking ridiculous. Hysterical, even. It's a basic ass rule that applies to all Liga teams. Barca haven't even signed anyone from Getafe, nor are Getafe or any other club actually obligated to sell a player if they don't want to. It's literally only, ONLY because Dembele is out for beyond the rest of the season. That's why it didn't apply when Suarez got injured. Barca currently have something like 17-18 fit first team players. You can't just pull everyone out of the B team, as they also have injuries and a complete fixture list to fulfill themselves. Plus as mentioned, the domestic registration rules aren't the same as in other leagues.
Honestly don't get the fuss being made about it. If you don't think it's a good rule, fair enough, but it's hardly Barca doing something wrong.