Seed audio input specs on data sheet (Rev. 7)

Electrosmith Products Daisy Seed
1

Hello there
I am designing an audio effects pedal with the Daisy Seed Rev. 7 and was studying the Seed’s data sheet and schematic. There are a few things stated there, where I was wondering, how they came about.
This is my first post here. Please let me know if I should place this post somewhere else or if I missed some rule or some information. Also, please excuse if some questions may be a bit nitpicky.

For reference, I’m looking at the data sheet v1.1.2 and the schematic of Rev. 7.

  1. The Seed data sheet states an input impedance of 30 kOhm (typical) (on page 6, next to Figure 1.2). However, I made the following estimation. The Seed schematic shows 3.6 kOhm resistors in series with the audio inputs. The PCM3060 data sheet (audio CODEC) states an input impedance of 10 kOhm (typical). This should give an input impedance of 13.6 kOhm (typical) (ignoring the 4.7 uF capacitors).
    → Question 1a: How are the 30 kOhm derived? Am I missing something?
    → Question 1b: What is the purpose of the 3.6 kOhm resistors? Is it for compatibility with solder Seed revisions?

  2. The Seed data sheet states the absolute maximum rating for the audio inputs as 3.6 Vpp. However, I made the following estimation. The PCM3060 data sheet states -0.3 V … Vcc+0.3 V as the absolute maximum for the inputs. With Vcc = 4.5 V (as stated in the Seed data sheet) and AC coupling this corresponds to 5.1 Vpp. If we to consider the voltage divider formed by the 3.6 kOhm resistor and the PCM3060s input impedance, the limit would even be higher.
    → Question 2: How are the 3.6 Vpp derived? Is it based on the 0 dBFS.

  3. Page 5 of the data sheet shows plots for the audio performance of the Seed. I is not clear to me, what these plots are actually showing. Is it the input stage: Is it the input side (analog to digital), or the output (digital to analog), or a combination (meaning the Seed in “digital bypass”). Interestingly, the plot in the current data sheet (v1.1.2, with PCM3060) looks identical to the plots in earlier data sheets (e.g. v1.0.5, with WM8731).
    → Question 3a: What is the measurement setup for these audio performance plots?
    → Question 3b: Is it possible, that the audio performance plots are still from an older Seed revision?