Not at all surprised by Dortmund's habit and I think as a business club they know what to do. Instead of giving Guirassy a long time, when an offer comes in from a big club and even wants to redeem his clause, Dortmund will be very happy to let him go.
I think it is still quite difficult for any team to match the prowess of Dortmund management when it comes to player business and it looks like they will continue to do so forever. What makes me wonder, are the fans silent about the behavior of their beloved club? even though if Dortmund wants to keep their players then it will be much easier for them to win the title. But again, being in the top 4 in the Bundesliga seems to be enough to make them happy.
That is one of the reasons why Dortmund find it difficult to achieve success by winning trophies every season and they prioritize business more than the club's success. Many players have been sold and on average they have quite good talent and almost all of them are successful at their new clubs. So I'm also not surprised why they plan to release Guirassy to another club even though his contract hasn't ended yet.
Fans also criticized Dortmund's management policies, but this criticism was completely ignored. I think this is completely related to business and the goals of the club do not think about the success of the club at all. Last season they had good moments in the Champions League but the lack of sufficient player support made them fail again.