> Starting a 'cold' debug session into a UI application may take 10-ish seconds until applicationDidFinishLaunching is reached, and most of that time seems to be spent with loading the symbols for hundreds of framework DLLs which are loaded during application start (which I never even need because I can't step into system frameworks anyway) - and seriously, why are there even hundreds of system DLLs in a more or less hello-world-style Metal application with minimal UI?

This is so you can see function names for system frameworks. You can step into them if you want too even if Xcode tries to stop you doing it by default.