Is this particular case, yes we don't want to specifically show different content on the web. And yes the notion of of sign in on the app is, I wont say onerous, is completely unnecessary. I don't see the maintenance of multiple hierarchies as an issue, by default we use two level navigation and nest a home collection if we need one level navigation.
Our client has an enterprise app and they distribute the content to their staff, they would like web access but need to restrict it. If they only way they can have restricted web access it to put a sign in on the app as well, then they will not use it.
Whilst this is the scenario they prompted us to think of this, we see merit on the idea of having different content for the web viewer, and have used this feature in DPS 2014. If you can have different content for the tablet and phone, why not for the web? For example you can use the web viewer with truncated content to encourage users to the download the app.
Thus we thought it would make a good feature request and suggested it