A certain Jim H, of uk.rec.audio "fame", writes :

Is it possible that, back then, the DACs were only effective up to a
certain rate, at a lower rate than for the ear? If, say the DACS showed
no improvement in sound past 44kHz, your experiment would always show
cd to bo optimal. Just a thought.

AFAIK (Dave P would know more about this than me) the early ADCs weren't
capable of 16 bits of resolution; they clocked in around 14 bits. I
always thought this was another good reason why remastered recordings
often sound so much better.

--

"Jokes mentioning ducks were considered particularly funny." - cnn.com