So, did anyone anemometer traverse test a 65 mm cylinder connected to a San Ace B97 fan?
Didn’t think so.
Anyone work out how the San Ace B97 fan that makes ~ 5 m/s airflow in a 65 mm tube manages 4 m/s at 1/2 power?
Didn’t think so.
Yes, Mizuno did, and so did the visitor with the propeller type of anemometer. It was ~16% higher than Mizuno's reading.
You are the only one who has failed to do this, as far as I know, so the problem is on your end.
I showed that the flow rate is correct by looking at 10, 30 and 50 W calibrations, and computing the flow rate mass per second = power / (temperature * specific heat). It was within a few percent of the measured value. Do you know of any problem with that method? If you don't, I do not think you have any reason to doubt it.