> APCA models how human eyes actually perceive contrast, factoring in font weight, spatial frequency, and ambient light — a genuine improvement over the WCAG 2.x formula. […] The research behind it is peer-reviewed and substantive

That's what the author claims, but I have not seen any evidence that it is actually true. In a ticket where they were asked to provide peer review, they instead linked to a bunch of blog posts that in my opinion do not qualify as peer review: https://github.com/w3c/wcag3/issues/29

Also, it is not as if the WCAG 2 formula would not model how humans actually perceive contrast.