The Marshall stock 2203 has the master volume *after* the tone stack. The PPIMV (post-phase-inverter master volume) puts it even further downstream. Jose puts it *before* the tone stack. Three downstream consequences:
1. The tone stack always sees the same level. With a post-tone-stack MV (or PPIMV), turning the master down at low volumes makes the tone controls behave as if they're scooped (the FMV/Marshall tone-stack interaction is signal-level dependent due to the cathode follower's loading). The Jose MV avoids this — the tone controls always work the same regardless of MV setting.
2. Diode clipping is shaped by the tone stack on the way out. When the diode clipper kicks in (at the MV wiper), the resulting clipped harmonic content gets sculpted by the tone stack BEFORE going to the phase inverter. This produces a more "vocal" clipped tone where you can EQ the clip itself. With PPIMV diode clipping, the tone-stack already shaped the signal before clipping, so the clipper just chops what's there — less control over the clipped voicing.
3. The phase inverter sees a (partially) clipped signal. This means the PI doesn't have to clip on its own — the distortion is "preamp dominant" rather than "PI dominant". When combined with the NFB-reduction mod (100k off the 4Ω tap), the power amp behaves as a clean amplifier of the already-distorted preamp signal, with just a hint of its own loose, sponge-y interaction. This is the Jose feel.