This isn't a defense, just an explanation... but it is also an explanation of why the entire idea of "we'll not give blind people a way past the CAPTCHA but just give a pass to 'real' blind people so we can pass ADA", which is that it should have been transparently obvious that this approach is completely infeasible and unscalable. As big as Google, Facebook, or Amazon are, they would struggle under the load of trying to create a system for determining who is "truly" blind... and that's still true if we ignore questions like exactly what "blind" is anyhow.
This shouldn't have gotten deployed and then become a problem; it should have been a 5 minute diversion in the meeting where it was proposed to analyze it's completely infeasible and never made it to so much as the design phase, let alone the deployment phase.
If you had a system for completely accurately identifying characteristics like "who is blind" in the presence of extremely hostile attacks on the system, you'd have something far more valuable than the CAPTCHA system itself! The whole idea intrinsically depends on having a stronger solution to the problems CAPTCHAs are meant to solve than the CAPTCHA system itself provides... it's fundamentally a logically unsound idea.
User POV :"Wow, provider is a really shitty entity and had no respect for my legitimate problem."
Provider POV: "We get a huge number of illegitimate claims identical to legitimate ones regularly, the system would collapse if we didn't do heavy triage, the problem is the level of abuse, not a moral bankruptcy on our part."
I suppose "this is why we can't have nice things" captures some of it.
That's what happens when trust erodes, and why we can't have nice things.
If anyone should be be more understanding and absorb the costs to appease the other, it's probably the big corp, not the little guy.