You are thinking that there is no evidence of Oliveira's grappling being integrated. You are completely wrong.
Do you realise that Oliveria just beat a better grappler than ANYONE Khabib has faced in the UFC. RDA is close, but Tony is bettter.
We have evidence of Oliveira's top and bottom game being well integrated, we have evidence of a solid takedown game, and we have evidence of his subs and transitions as well.
I agree with your point about the lack of evidence not being evidence for Khabibs bottom game, but you have to understand that Oliveira is using a traditional BJJ background, and will spend far more time on his bottom game than Khabib will. That alone is enough for me to say Oliveira's bottom game is better, just like I am saying Khabibs wrestling is far better.
As I say, I agree that Khabib is a better grappler, with far better wrestling and chain wrestling. But, Oliveiras bottom game better, and his top game has proven to be incredibly nasty, and not all that far off Khabibs.