Website work
A website has to explain what the project is, why it exists, and whether the person behind it has thought carefully enough to be trusted. That is mostly public-facing communication work.
It also needs SEO-friendly pages, readable articles, and a stable identity surface for future writing.
Web app work
An app is where state, permissions, sessions, and user data matter. Once a user is inside, the priority shifts from persuasion to execution.
That is why the app host should stay visually and structurally simpler than the public site.