I would have liked to see that as well, particularly as he called it out as effectively broken.
But I do think the onus should be on manufacturers to engage with the community rather than the other way around. One has a PR department, the other is some guy testing kit in his front room.
Another manufacturer (Denon IIRC?) did the same after a poor set of measurements was published, worked through them and identified a firmware fix, for instance - not just put out a PDF saying "No you're wrong, look at our totally unbiased measurements" and then (again, allegedly) stonewalling the reviewer.
I'm not siding with anyone here - I respect ASRs reviews as much as I do the ones here, and if I were to consider an AV40 I'd respect my own in-home demo more than any of them.
And I would consider an AV40 if only for the reason that it would be trivial to take one home for a demo to see for myself - but the approach here by Arcam reminds me a lot of a broken NAD AVR I sent back eventually - i.e. "must be something about YOUR setup that's broken, because our AVR certainly couldn't be".
Manufacturers engaging with the community is a double edged sword but alot of people believe they should and doesn't seem unreasonable to me either.
Denon went to the trouble of pointing out the downmix issue to Amir and were effectively rewarded with an updated review. The SDP-55 review (Identical firmware sister unit to the AV40) effectively rights the mistakes and explains the ground issue that was referenced by Arcam. I suspect if Arcam had gone to the trouble of explaining how to correct the measurements the review might have been corrected.
Definitely still some bugs left but unlike NAD firmware updates have been actively addressing them (I know this because 5 of the IMS references in 1.46 release are for bugs I raised in Dec/Jan).