I mean, I've read the novel, seen every adaptation of the show and I still don't really get what ur hinting at. Are u saying that NHS learned how to sneak from JGY? Or thay NMJ told everything to NHS? I mean, unless I missed some crucial point somewhere (i did consume everything pretty fast) it's unclear as to why or how NHS knows everything (I mean it's heavily insinuated that he orchestrated Wei Ying's resurrection to avenge his brother but it's still technically not cannon) :/
Nhs knew from the start or close to that what jgy was planning. He always had his suspicions but he didn't really do anything. Since nhs and nmj are close tho nmj is always talking at him, nhs of course got mad about the fact that jgy had killed his brother. So, every year, every day, slowly nhs plotted his revenge against jgy but pretended that he was dumb. The moment lxc started looking away from jgy when they all were kidnapped, nhs lied and said jgy tried to stab him but in reality jgy got stabbed instead. But at that moment who would believe jgy, the villain, or nhs, the stuttering nonsense. Later after their release wwx talks to nhs and reveals in a playful way that nhs is not what he seems which means wwx found out the truth about nhs
And THAT is why nhs knows everything