Legacy URLs such as /public/... and /private/... are now emulated to determine the best resource with the same resolution algorithm, but instead of displaying the page, it will make an HTTP 302 redirection to the correct URL. This handler is present in the controller configuration. There is a noticeable difference between two routes.
The public redirection attempts to find a node with the legacy resolution algorithm without authentication, which means that secured nodes will not be resolved and the redirection of a secured node will likely redirect to another page. For instance, resolving the URL /public/classic/administration/registry path will likely resolve to another node if the user is not authenticated and is not in the platform administrator group.
The private redirection first performs an authentication before doing the redirection. In that case, the /private/classic/administration/registry path will be redirected to the /portal/groups/:platform:administrators/administration/registry page if the user has the sufficient security rights.