Okay. I do things a little differently, admittedly, some folks would say they are unsafe, (and perhaps they are)... BUT -
How was this bird housed in his previous place? By himself, or with other birds? Because if he was by himself, locked up in a cage, alone in a house for the past 20 years - Hasn't he, by definition, already spent the past 20 years in quarantine?! Am I missing something here?!
My rule of thumb when I knew where a bird was from, and the vet tests looked fine, was to let them out and put them on the big playstand. They've done enough time in solitary.
If there was no history, and we didn't know the exposure, then quarantine is called for.
"You can't be too careful..." is kind of wasted advice when given to someone like me. I have always taken calculated risks. It's in my nature. So consider the source...