Might also be possible the guy who designed it has hearing loss and can’t hear the usual 75dB noise or even 80dB.
Hearing loss is another sad story. My dad has hearing loss and now has to spend $4K on his hearing aid devices.
I hope you got him a hifi hearing aid, though that will likely cost over 7 to 8K. If he is not crazy like us about sound quality then I guess a 4 K device is find as long as it is of good quality with no annoying noise. I would likely consider those hifi hearing device when the time come. To be fair to Anthem, I do think it is a mistake to have the sweep tone so loud at 85 to 90 dB, when it did the sweep for time delay measurements it definitely was louder than 90 dB peak, the duration is not long enough to cause hearing loss unless someone keep doing the calibration all day long and day after day. No one will be that crazy, not even me.
So it is more of an annoying thing, and the only benefit is for better SNR, but that is the silly part, because whatever accuracy they can get, it will be completely erased/offset by other elements such as the mic, mic positioning, room ambient noise, user's errors/imperfection in their procedures etc.
It would be better, if they are really concerned about SNR, that they use a pop up warning that the level is too low, and that's how Dirac does its. That's really not problem because Anthem ARC is custom build for all Anthem AVRs/AVPs, so they have full control of the volume/level output, same as Denon, Marantz, Yamaha and Sony's, so the output level is set regardless of the volume setting. I am sure YPAO works the came way, that the users actually have no control of the sweep tone level regardless.