Because the test folder was missing I compared parts of code which I considered having effect on unloading decisions in objc4-680 and objc4-706.
I see that the extra dlopen() call is now gone from objc-os.mm and is nowhere to be found in the source.
Also _hasObjcContents private function while still defined is not used within the module anymore.
It’s still possible that the unloading logic has been moved outside objc4 but I didn’t go that far to investigate more.
Thanks to your pointers to objc runtime source I found I might use some environmental variables to get better idea what exactly is causing the problem.