The ocular powers necessarily don't denote the jutsu. You've Itachi's eyes in Sasuke's sockets yet he never uses Tsukiyomi. Reading the manga without missing the details is important here. We got Madara claiming he couldn't absorb a Sage Art Rasengan through the "Preta Path" he possessed yet we have Pain's Preta Path efficiently absorbing all kinds of natures and techniques as the Databook hyped it to be with no repurcussions or limits unlike what we see with Madara. Then we've the fact Naruto Villains utilize prior acquired techniques in an upgraded manner; eg:- Raikiri being utilized in a merged formation with that of Kamui after accessing and being amped with that of Rikudo's Chakra. It's common sense really. No point in arguing a logically pre-established fact. Manga reiterates the name "Pain" whenever the paths are in mentioning like we've seen characters such as Naruto exclaiming on how Nagato possesses all the paths of Pain and not "Six Paths of Sage" like headcanon and personal interpretation suggest. It's blatantly clear at this point. Six Paths Techniques are multiplicatively used in reference to several of things like Six Paths Chakra, Power & Sage Mode and The Black Rods of The Gedo Mazo. It cannot therefore be solely appriopriated toward the Title of The Rinnegan, alone. Numerous Manga Scans support this basis and have been substantiated by them.
It's really a matter of logic and just that; nothing more. Reading the above written one could never repeat the old school argument ie, it's plot. As "plot" literally pushes the notion of pre-acquired technique being boosted to a new level when character X gain new, stronger levels of power.