How Does El Capitan Improve Application Load Times?
Barring magic the only solution of load time should be to load an app in the background (completely or in part), so that it can load faster when called up by the user.  Obviously application developers can work on their app to make it load faster (like Libreoffice did) but this seems to be a completely different story. Preloading apps obviously has the disadvantage of taking up resources and it might only work with the apps bundled with the OS because these are the only apps that the OS developers can actually directly control.  In any case, an excellent question, and I am sorry I cannot provide more info.