How important is +- 0.1 db from RIAA curve?

For example here is an excerpt from an interview with Conrad Mas of Avid.

Conversations with Conrad Mas of Avid HiFi:
7. Could you talk about the RIAA curve you chose and how designing a RIAA section is not such a trivial matter?

... When we looked into this matter further, however, we realized that most recording studios whilst sticking very closely to the standard curve, used treble emphasis limitation in recording for decades (there is a quasi-standard defined by the leading record-cutting-machine manufacturer Neumann). Applying a correction according to Neumann standard makes a small but very audible difference. Whilst it's important to follow the RIAA curve, not doing so only alters the tonal balance of the sound; there are actually other items and components within a phono-stage that alter or make a bigger sonic difference than slight deviations off the correct curve. For instance if you played a record that was not cut with a perfect RIAA setting, say 1 dB difference between 1 K and 5 K, you'd be hard pressed to even notice. If we, however, changed the type of capacitors used in the phono stage, there would be a much bigger and totally noticeable difference.

Note: Avid phono stages are Neuman HF corrected, it is stated in their specifications.