I have no idea what was the interaction between AVA and Stereophile in the past, Stereophile may not like AVA because it isn't expensive enough.
Or it was just an honest mistake. When JA was listening to and making measurement on the speakers, he was focusing on the speakers, not the rest of system, not the amp, preamp, CD player, or turntable.
If he was reviewing an Hafler amp modified by AVA, he'd better not just say it's an Hafler 500 with better sound.
Or it was just JA's writing style, when he saw the amps were label Hafler, in his mind they must had been Hafler, and didn't think much of it, not a big deal. It's a speaker review, not amp review.