I read that one already but it says nothing conclusive about calibration with the mobile app or the receiver.
So far only the MultEQ-X app has correction. It will show real physical distance measurements in its UI, but it will put them into the receiver with the 0.875 adjustment.
If using the normal Audyssey app, or the receiver itself, or a tape measure, you should make the 0.875 adjustment yourself.
It does accurate measurements - the problem is that internally, the speed of sound constant that is being used is slightly off. Who knows why, but it was discovered by a user at AVS and confirmed by others. The workaround adjusts the timing to close the gap.
Yes, that speed of sound constant means an inaccurate conversion of entered distance to delay.
I believe the reason why is just that 1ft = 1ms = 30cm was a reasonable approximation when older D+M AVRs only had 1ft/1ms/30cm distance adjustment, maybe 20 years ago. It didn't cause any appreciable error within the adjustment granularity available at the time, and it kept the maths simple.
When they refined the adjustment granularity to 0.1ft/0.1ms/3cm, that approximation was no longer good enough - lots of people will end up with 0.5ms error, thus not achieving the expected 0.1ms accuracy.
The flaw is really surprising it was there at all, and not really shown to exist until now with all the people that take pre/post Audyssey measurements. I haven’t followed it too closely, but has Denon/Marantz acknowledged the issue yet?
The problem is independent of Audyssey. And it doesn't really show up on any frequency response, which is what most people are looking at. Also many pre/post comparisons will be done by turning Room EQ on and off, so keeping the timing...
Don't think D+M have said anything.