This is false, RSM by definition belongs to Hagoromo. Six paths Ten Tails coffin seal (which Madara and Obito had) is NOT the same as what naruto and Sasuke obtained. otherwise Obito should have an enhanced rinnegan the moment the juubi was sealed inside him and Madara got the rinne sharnningan. Which Obito couldn't get as he didn't have both rinnegan (nor was he Kaguya).
You must be registered for see links
also In order to make the truth seeking ball one needs six paths senjutsu (which only Naruto and Hagoromo had) and it's been classified that Kaguya, Hamura, and Toneri didn't have six paths senjutsu so this leads to the fact when one has mastery over all the elements (plus yin-yang release) with a massive amount of chakra and skill in shape transformation, one can ultimately make a TSB. TSB are not from Bijuu exclusively but from when one has six paths senjutsu or what I said in the latter. Also Naruto's RSM was above what Madara had as Naruto was able to outmatch Madara in strength and he even was able to dent Kaguya whom had a much more Dense and multiple times more massive of chakra than Madara even though she did not have six paths senjutsu.