Differences with the input stage on the zvex Box of Rock and the Box of Metal

[mordechai]

I was looking at the schematic on madbean for the zvex box of metal, the link for which is below:

http://www.madbeanpedals.com/projects/Kokbox/docs/Kokbox_ver.3.5.pdf

The input stage is very similar to the box of rock, insofar as it is based on the SHO, though there are some notable differences.

For example, the BOM uses 2.2M resistors instead of the 1M on the BOR.  I imagine that this is for higher input impedance...to preserve high end as it goes through several more MOSFET stages than the BOR...is this a fair guess?

It is also missing the 470k/470pf parallel stage, though I assume that this is because it is not attempting to emulate the tone character of the Marshall JTM.

What I am confused about, though, are the two resistor and two caps that follow and which come before the next MOSFET stage.  What purpose do they serve that would be ill suited for the BOR?

And tangentially...at the end of the circuit, before the output, is the 10uf cap and the 100k resistor there to roll off low end?  Why not work that into the tonestack stage, or is the circuit just too inherently bass heavy without that?