So boruto got this eye called Jougan (damn thought that was going to be some kind of villain), from his parents. So basically: Naruto's Negative Emotion Sensing + Hinata's Byakugan = Jougan, that's cool. Basically all the Hūyga were doing before was keeping the eye in the clan, ain't surprised a mutated eye came out of it, when a Hūyga branched out.
Bijuu abilities (as far as we know) can't be passed down, but their chakra and attributes can. The Negative Emotion Sensing was Kurama's power, until Naruto took his chakra and made it his own therefore also gaining that ability, which (as is now being said) was passed down to Boruto, which mutated his eyes. Sorta like how Hashirama's wood release (well Yamato in this case) was also changing when it came close to Naruto's chakra.
For those in denial about the NES not being Naruto's power, explain Mito. As far as we know (and that's what's been shown in the Manga), Naruto is the only one who did what he did to Kurama. So how did Mito get it?
On a side note Anime =Filler :Sparks:
Edit: The author seems to be confused him/herself so I'd personally take this with 3 bags of salt. He's speculating himself smh. Trust 123filler to take this seriously.