The new Page manager existing pages-module fills a need when working with modules that do not have ctools support and have their own paths.
Page manager (ctools) out of the box respect modules existing paths (unlike Views), but sometimes you have the need to override them in different ways, and with Page manager existing pages the original page call back could be reached by the content type plugin.
On NodeOne we use ctools a lot, and I could think on some user cases this new module could be really useful, instead of doing custom code.