Note: It seems like “keeping the URL” for 301 is not very well defined.
In the setup process (when resources are detected), one step is dependent of the other. Only the resulting calendar/address book URLs are stored while all the other URLs (current-user-principal, home-set etc.) are thrown away at the moment. So, the only URLs where 301/302 could make a difference are when the URLs referenced by
calendar-home-set are redirections. DAVdroid stores the URLs given by PROPFIND on the home sets and doesn’t check for redirections at this moment, so there are not redirections to be handled.
In the sync process, settings aren’t changed nevertheless so all redirections can be treated the same way.