Well yes thats how he voices them. The SS is just very loosely based on Steves 69 plexi face jmp.
Its more of a modded JCM800 to be honest but with the thicker voicing of an older 60s marshall due to a wise choice of resistor and cap combinations in especially in the 2nd gain stage.
All of them, the JJ, BE, SS, X are based on 800s with the gain pot later in the pre amp and just different plate snubbers and different resistor and cap combos on the 2nd gain stage. The SS is the most JMP like because its the 2.7k/0.68uf combo. Where the BE has a higher resistor value with different a voltage divider.
If you look at a JJ it is has a different depth circuit too.
You could say that the Jose amps are also similar. They just have the gain and master controls in different places in the circuit (each control is one stage earlier) making it more fiddely to set right but they are also just JMPs with additional gain stage making them more like 800s too. So Jim Marshall created a modded JMP on his own and called it the JCM800. The only differences are the depth circuit, master control layout, the trannies, gain pot location and bright caps. Its 85% there.
The friedman stuff however is pretty much perfected. If I run the presence up high enough I dont miss my old JCM anymore.
A good thing to do on friedmans is dropping the PI fizz cap from 100pf to 47pf and putting a bright cap on the gain. Also change the screen filter caps from 2x32 to 2x47 which makes them even more direct. If you then cut the 500pf on the 3rd stage you are getting back a lot of the kerrang and spikes in the treble response that you might be familiar with

.
Changing the depth cap from .0047uf to .0033uf also did something for me getting the mids closer in the upper region. Play with the depth circuit, you'll be surprised.
From there it doesnt get much better anymore. You now have very much a perfect british style rock amp with tons of articulation that is easy to play and sounds good recorded and in the room.
I suggest lower output pickups or pickups with a tight or lean bass response like in traditional LPs.