[Pharo-project] Why some packages are rejected from Test Coverage?

Ok, I see that there are some packages that are not able to be selected to run test coverage. I noticed that they were big packages and then I saw the method: TestRunner >> promptForPackages where you can see it rejects packages like Kernel, Collections, System, etc. I guess because Test Coverage may take long time in those big packages....but I don't know if that's a good reason to disable them. Maybe a popup saying "Are you sure you want to run Test Coverage over this package? It will take a lot of time" is better. At least VisualWorks does something similar. What do you think ? Cheers, Mariano