I think they're talking about "Deku was born with a quirk, but it was stolen" theory: https://www.youtube.com/watch?v=MvxtHbt9vQc&t=433s
But they did explain why it is so ri8?.. His both parents have weak quirks so much that they can't even be used all the time.. Also they said about the great phenomena research, the pinky toe joint one.. The ones who manifest quirks have 1 joint but Deku had 2! There was 1 thing i didn't get though, about Deku's parents being 4th generation. What is that?
I know yet the doctor who did the radiograph showing Izuku's toes is the same doctor who was working with all for one .
Maybe this x ray is a lie ?
You remember all for one brother ? He was thought qurikless but he did have a hidden quirk :/
And the winged nomo who singled Izuku out of the crowd to kidnap
It was confirmed that this nomo has the quirk of Izuku' childhood friend
something suspecious is going on ..
This is true.. All for one thought his brother was quirkless so he bestowed on him a quirk with enhanced physical power/stoaage of physical power. But the brother had a quirk to transfer quirk to someone else so both quirks mingled and All for one came into existance. This was told in one of the chapters.
All those nomos has the power of regeneration .
I have the feeling that it is deku's stolen quirk