I hope Barcelona does that especially to sell De Jong. How could their club's finances be so messed up just to pay one player every week? If I'm not mistaken De Jong's salary for that week was 730k Euros and it was very unreasonable with his less consistent performance and frequent injuries making him the player with the highest salary at Barcelona.
It is possible that Hansi Flick should give advice to management to sell some of his players and he can target the players he needs in the squad. Because this is his first season managing Barcelona, he will definitely be careful and not want to make a mistake. Full trust in him must be repaid by winning one trophy at least next season.
Apart from being able to reduce the salary burden they have to pay, selling De Jong will also give them benefits because currently De Jong is one of the highest priced players they have. So it will give them a bit of a financial boost, yes although they will definitely use that money again to recruit players, but as I said before that will reduce the salary burden they have to pay.
Now in my opinion the decision is in the hands of their new coach, if their new coach can provide advice to management and can convince him, then De Jong will be one of the players on the list to be sold. Moreover, we also don't know whether this player fits into the coach's playing scheme or not, because usually the coach has his own criteria for the players he needs.