The Dr. Z Maz uses a cathode follower circuit, like a '59 Fender Bassman, or vintage 60's Marshall or Vox.
That circuit and tone stack model was used in the tweed Fender Bassman, then copied in Britain and it became the Marshall JTM45 and 50 watt and 100 watt circuit and the Vox AC30 circuit in the 60's.
I know Dr. Z's early amps all used a cathode follower like a tweed Bassman and were modeled on that Bassman, Marshall, Vox tone stack and cathode follower circuit which is difficult to add reverb to, altho Dr. Z did find a way.
The cathode follower combined with the Bassman style tone stack is an absolute must if you're going to build an amp that sounds like a '59 Bassman, Marshall or a Vox. But none of those amps had reverb originally and the cathode follower circuit doesn't provide an easy place to insert reverb in the circuit.
The blackface Fender circuit works great with reverb and sounds great with reverb, and even when the reverb is turned to zero it adds gain to the amp, rather than take away anything.