I don't know that that's ironic. Doing accessibility testing without significant impairment is very, very difficult, because you take shortcuts an impaired user doesn't get to use without even realising it. An impaired user can "just" try to use the software and they'll smash their face straight into all the roadblocks and sharp edges.
But a sighted user will be much less proficient at using anything like that, so it is probably better to find someone who isn't sighted and so does everything like that. Otherwise it will take far longer to recognise any issues
Not only that, but they'll be stumbling around not really knowing how vision-impaired users actually work with their devices, so they would have issue an impaired user would not have, and not hit issues an impaired power-user would.