"This is far-fetched, but maybe he just did not like the Bel Canto amplifier?"
Of course that is always possible.
But, to achieve best results, first it would be beneficial to make sure things are set up well to enable a comparison of what each piece is capable of, rather than what each piece just happened to deliver.
I know what the Bel canto ref100mkii is capable of with proper setup because I have been through setting it up. I also believe that without the proper setup, teh results could be quite unimpressive.
Exceptional things usually require some special preparation in order to receive the benefit. That is definitely the case with the BC amps based on my experience.
I've never heard the Threshold, which I am certain is a fine and surely different sounding amp as well, so I cannot offer anything there.