But maybe people don't care about apps starting fast on their macs anymore, since a lot of them come with SSDs :)
I think the GP post was simply referring to the fact that a vast majority of software is 'installed' on the mac. Just drag it to the application folder. And drag it to the trash to uninstall. This almost certainly means you have a bunch of duplicated library files on your computer, but also means each app doesn't have any external dependencies.
Yes, the App Store rules would prohibit apps with external dependencies such as that one, and at least for self-contained apps distributed through the app store, Apple themselves would be paying for the bandwidth resulting from their own poor decision, so an argument could be made for both ways.