PATH_INFO is a part of standard HTTP request and was used as poor's people beautiful urls when we didn't really understood how to configure an apache server to do URL rewriting (good old days).
But we add to introduce quirks in nginx configuation to support that and those quirks are now in conflict with front router deployment, especially when we want to transparently replace old ".php" scripts by routes.
Note: this has a good potential for random breakage everywhere in core because as soon as an url was written like /path/stuff.php/... it needs a special treatment. The very good news is that /path/stuff.php/?group_id=1 was managed transparently but should be fixed after this patch.