That's very revelevant. It's proves that having the TSB doesn't mean you have onmyodont. What you said is like saying "having the ability to create wood mean you can create any wood jutsu". We all now that's not true. Onmyodont is a unique that requires the TSB to use.
Maybe i phased it poorly.
Madara had TSB which in turn erased minato's arm despite his SM, so he has ohnoyoudont
Then we had naruto who recently got sage's chakra and in his base BSM mode was able to kick it back w/o goin into sage's senjutsu mode, so sages chakra is high quality senjutsu on it's own.
Sasuke also received same sage's chakra, that proven it's senjutsu qualities via black chidori, he later was able to stand on TSB platform w/o suffering regular erasing effect.
If naruto had onmyoudon on or not i hardly relevant because it didnt even erase sasuke so it cant negate what it cant erase, as seen with BSM base naruto.
End conclusion is that sage's chakra is senjutsu in itself thanks to big share of that fruit chakra he got from mommy and sage's senjutsu is mastery over all KKGs - TSB.
Makes sense?