Yeah, if you have a non-trivial big project that you don't know how to do yet, then the only thing you should be estimating is "Create a design for project X".

Yeah, if you have a non-trivial big project that you don't know how to do yet, then the only thing you should be estimating is "Create a design for project X". After that, you might need new tasks "Create a design for sub-systems Foo and Bar". Until you have spent time on design, there's often no point estimating the total project.