the GPL revocation requires violating the license terms and it’s a clause just to prevent people from using GPL code and not giving back their code. The GPL allows your fiercest competitor or enemy country to use your code and you can’t revoke the license as long as they publish their code too.
the FUTO license can revoke the license just because Rossmann says so. It is a mechanism to keep Rossmann the owner of everything that spawns from the code of the app and being the only one who can make money from it. If Rossmann doesn’t like someone who wants to redistributes the app, he can immediately revoke their license. Which is fine for a proprietary app. The issue is that he keep calling it “open source”.