Rebuild is necessary for things as trivial as changing the default install path. It's absolutley standard; a Linux distro that doesn't rebuild packages somewhere would almost not count as a distro.
Hmm. All the various Ubuntu derivatives (eg, Hanna Montana Edition or Christian Edition, or even Kubuntu and MATE Editions) that change some defaults without rebuilding packages... don't count as distributions?
This is somewhat tongue-in-cheek, but it's actually a question I don't have a solid yes or no answer to. I can see it both ways.
If your users are pulling software direct from the upstream distribution then you're not a separate distribution of Linux, you're a 'spin', 'edition', or an installer.
This does get a little murky when some of the packages are distributed directly but others are pulled from upstream like Antergos but the changes are so minor that I would still consider it an Arch spin.
This is somewhat tongue-in-cheek, but it's actually a question I don't have a solid yes or no answer to. I can see it both ways.