It all boils down to sighted people deciding that they know best about what a Blind person can and can't do.
So many blind people are questioned and doubted every day about whether they are "REALLY" Blind or not.
I'm one of them.
It us extremely rare that someone who is Blind (The current UK terminology for "Blind" is Severely Visually Impaired) has no useable sight at all, at an NPL level (No Perception Of Light).
Because of this, we are often called "Partially Sighted" (which means you have some sightloss, but still quite a fair good amount of useable sight remaining), or even accused of faking or exaggerating our blindness, Simply because a sighted person (or a group of sighted people) have decided that (in their obvious, expert knowledge of not living a single day with sightloss), the thing they have just seen the Blind person do, Shouldn't be possible.