Dear Eldartford: +++++ " You are correct that importance of RIAA frequency accuracy is over rated. The rest of the system, notably speakers, are much less accurate. " +++++
yes, even some cartridges specs are less accurate and this is one way to see that RIAA accuracy.
My overall/whole point of view is different and different not only on the RIAA accuracy but in each link on the audio system chain: almost all of us ( I hope ) want to be nearest to the recording and trying to achieve this goal we need ( between other things. ) accuracy, very low noise, very low distortions, etc, etc. trying to add the less and trying to lose the less all over the audio system chain, at least this is my goal ( of course the enjoying of the music. ) maybe yours is different.
Now, what is the inverse RIAA eq. curve? well it is the main factor why phono stages are a necessity where IMHO the main target in any phono stage must be to deliver an accurate inverted RIAA curve to mimic the one used on the recording to give us a flat frequency response with the gain/low noise/low distortions that our cartridges are asking for.
I don't care what happen after or even before the phono stage link the subject is that in that phono stage things must be working/processed with accuracy in the right way.
If I was thinking like you that there are other audio links with a higher un-accuracies then that spec could be +,- 3-5 db and no body cares anymore about.
But things are not so easy, the RIAA is a curve not a flat line so any single deviation in that curve ( at any frequency ) affects not only that deviation on that discrete frequency but affect almost three octaves!!
Do you think that you can hear a 1db deviation on the RIAA curve at 3Khz?, certainly yes because that deviation affects a wide frequency range and puts a continuous coloration in the sound reproduction ( of course that are people that does not care about, well I care. ), Eldartford I don't know how good are your ears perception but I can tell you that you can ( if your system has the resolution. ) hear even deviations as low as 0.1-0.2db
If that 3Khz deviation was the only frequency that was affected then you maybe can't hear it or detectec it.
Everything the same IMHO the RIAA accuracy makes a wide difference in the quality performance on almost any audio system.
Regards and enjoy the music,
Raul.