This is all assumption from me, but I think a lot of testing would likely be diagnostic machines and specialized testing – not actually playing games. I would assume it’s something like plugging in, confirming the parts all meet spec after whatever the refurb is. That spec is probably more around frequencies, power use, temperatures.
Obviously that’s not good enough if they’re sending out these clearly broken refurbs.
Sure, they obviously are dropping the ball here, just trying to explain what they might mean by “thoroughly tested” and why it’s not succeeding