HI IGS T1 - I agree with your comments 100% and you certainly seem to be on the case with Apple
Just to give you some further info ...... I purchased my first 6S on the day of release (25 Sept) and soon noticed the issues previously described, which are not evident on my wife's 5s (albeit an older, though still currently available model).
I spoke to several Senior Apple Advisors who were in communication with their Technical Engineers and whoever I spoke with, they always claimed that it was the first time they had personally heard of the issue. Whilst I don't doubt their integrity, there does seem to be an issue with internal communications at Apple, if colleagues are not being made aware of current issues.
On one occasion, I even had an Apple advisor playing music on a 6S in their office and it too had the same issue. Surely this should have been enough to confirm a 'potential problem'?
I have had to jump through several hoops, including uploading a video capture of my device playing piano music and increasing the volume to show the fault, direct to the Technical Engineers at Apple.
That was 2 months ago and there still has been no update back from the Technical Engineers.
I took part in the Public Beta testing program (and continue to do so), providing feedback to the iOS development team. Once again, no update regarding the 'speaker' issue - despite my feedback on the issue.
Clearly, Apple definitely know about the issue (since late September) by now, but still haven't addressed it.
After 2 months of being advised to keep replacing my phone, and no update from the Engineers, I must confess to having 'given up' in my plight to try to assist Apple.
Hopefully this background will be of benefit and assist you when you next speak to your Apple representative.
I look forward to a positive outcome for all