After reading the blog, I can offer up several rebuttals
Trackless Step is good but Ikki himself was able to see through it before he could adapt to it, meaning it's not infallible. Yujiro shouldn't have too much trouble getting past it.
Ikki seeing 100 steps ahead is taken out of context. One, it's said by a commentator, a person who's known to hype things up. And two, it's explicitlu said that he sees that far ahead because it's Stella, the girl he knows inside and out because he knows her insides amd outsides.
The precog is legit, but it gives him a flash of the future, and when he did it, he was woefully unprepared for it, as he miscalculated Stella's strength and he would've easily died if it wasn't for that vision. He's not Xatu with it.
...even after reading that blog I'm not entirely sure how Perfect Vision works. However, it's very explicitly said that it takes Ikki a whole minute to learn someone else's techniques, and Stella having her techniques so fine tuned made him take a while two minutes thirty seconds. Yujiro is >>>>> Stella when it comes to skill.
Ikki has really good timing feats. The best one I saw on the blog was where while blind, he was able to calculate how long it'd take bullets to leave their chamber when shot at him so he could dodge perfectly.
There's also the fact that besides Edelweiss, nobody in Rakudai approaches Yujiro in skill that Ikki fought.
Oh and the "thousands of years in an instant" growth thing was an obvious hyperbole/flowery language statement in the blog. And it's never said that Ikki mastered all martial arts. It's only stated that he knows many martial arts. It might've used mastered instead of many, but it didn't say all. Finally, I didn't see anything about him taking one look and knowing everything about the style of fighting the opponent has. If it's the Ayane thing, it's taken heavily out of context.