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Quite common.

He had an 02 sensor that would not read lean enough to pass the Air Injection self test . On this test , the DM looks for the 02 to go way lean when the pump comes on, verifying pump activation and system check.
So, an 02 that does not read as well as it used to shows up as an air code way before it shows up as a bad 02 sens code. Which will eventually happen...
The diagnosis was correct.