Maybe not fundamentally flawed but audio ABX testing is focused towards short term memory and opinion (especially in unskilled subjects) than I would like. I don't think there is any right answer to audio blind tests.

I'll trust actual validated limits of human perception such as 16/48 audio, 1~3dE colour, etc. And techniques used in video encoding like psnr, ssim, etc are also pretty well grounded in science. Also SINAD

But anything involving a human blindly comparing audio is into audiophile pseudoscience territory, no matter how large a cohort of people or how it is executed