It only goes through "apt the program", but apt is just serving as a method of installing a package, which is hosted on one of the configured apt sources.

Calling all software installed through apt "first party" is a wild stretch, since you can apply the same logic to git, wget, or a web browser. For instance, it would probably be correct to say that most Windows software is downloaded and installed through Chrome, but nobody in their right mind would claim Google owns the largest first party store for Windows.