That was a fan-fueled rumor and Nintendo never gave any indication of such a mechanic.
Well technically it had actual basing since Emily Rogers leaked it and she has been trustworthy source.
When it comes to what he said about female Link as well as his argument as to why Link is right handed in this game (you input attack controls from the right side of the controller so it feels more natural), I don't think Aonuma is really trying to make a valid argument, he's just trying to avoid saying something so blunt like, "We're doing it this way because we want to, it doesn't really matter. Shut up, you annoying fans."
Like, I imagine the only reason he said anything on the matter was because this non-existent thing that wasn't going to happen has been hyped so much by people that he sort of had to say something, even if it's dumb. I know I'm tired of all the talk about the possibility of female Link. We have Linkle in Hyrule Warriors but that's not exactly the same as she's her own character with her own story, people are wanting gender options for Link.
I don't think we'll ever have gender options for Link, just like we won't ever have gender options for characters like Mario, Donkey Kong, or Samus. We have games like Pokemon and some Fire Emblem titles for that.
The joke is that he's gotten called out for it because the best answer actually was just "we didn't want to." Like he could say that and everyone would respond with "okay." Like, we'll still advocate for it, because I think it's a cool idea, but most if not all people aren't going to get up in arms over it.
Obviously, the reason Link is getting singled out is because unlike Mario, or Donkey Kong, or Samus, he changes every game (okay Donkey Kong has changed over the years but it's still different). So the best argument is still 100% just Aonuma not wanting to do so. And really, that's the main takeaway from this. Aonuma sees Link as a guy, and he just doesn't want to change it. That's basically what he should have said.
If he's not sure about what to do with Link, he can always just put him in a tower like they have with Zelda for years. lol