I disagree, clubs and agents help each other out all the time. While obviously other clubs wouldn't give them the money they wanted, they would still help them offload players.
Italian teams do it all the time between each other and that Pjanic/Arthur swap deal from last season was just a way for both clubs to balance their books. I've mentioned it before but Juventus exchanged Spinazzola to Roma for a 20-year old left back who they immediately loaned out to Cagliari and then to Genoa, no intention of ever using him. It was a book balancing deal and also I believe a wink-wink deal for Zaniolo in the future, but then Zaniolo had two ACL injuries.
I'm sure Barca could easily find a partial salary loan for Coutinho and Pjanic, find a taker for Braithwaite, been less demanding with Atletico in that Griezmann exchange deal, but like you said instead of doing that they actually kept bringing in players