No its not an opinion, it was debunked by the RAW. The chapters you read are written by the translators, the original words are in the RAW. This isnt the first time the translators **** it up, for example they wrote (possibly because it seemed "more poetic") that Kabuto said "I will learn the secrets of RS" when in fact Kabuto did said "I will unlock the mind of RS" which can mean 2 things entirely.This is interesting and the first time I heard of this. Where or what in your opinion is the most accurate translation on the internet? And what does Tobi mean by second and third rikudou then?
Tobi said that he having Senju and Uchiha powers was the Nidaime Rikudou (second Rikudou) and then said that Nagato was the Sandaime Rikudou (Third Rikudou). This is why it is implied heavily that to unlock Rinnegan you have to mix Uchiha powers with Senju DNA.
Madara said something along the lines "Now having both the powers of the Senju and Uchiha in one body I am the Second Rikudou" in the same chapter he got the Rinnegan then in the same chapter he recognized Nagato's strenght and called him the "Third Rikudou" now unless there are 2 ways of becoming Rikudou it appears that becoming a Rikudou = having the Rinnegan and for that you need both Senju and Uchiha powers. Though this chapter would tell you that Nagato is the equivalent of Kakashi in Rinnegan since Nagato unlike Madara couldnt turn off the Rinnegan neither use the super haxx techniques like the meteor.