The matrix doesn't not do it because it's neutral, it doesn't do it because it's ss. A non neutral ss amp won't do it either.
The Matrix doesn't do it not because it's SS, it doesn't do it because it's a voltage amplifier with low output impedance and efficient negative feedback. Which is how neutral amps are made. It is not practically feasible to build a neutral tube amp. Which, in turn, is why you will not find a tube reference amp.
All valve amps needs an output transformer. ss amps dont have output transformers. it's that op transformer interacting with rhe speaker load that is the difference.
No it isn't true. Sure, output transformers are part of the problem, they introduce their own distortion and phase shifts which make negative feedback on tube amps less efficient/more difficult to do, but they are not the sole or even the major difference. Transconductance amplifiers just cannot dampen speaker resonance as effectively as voltage amplifiers do. You can make a solid state transconductance amplifier which will behave like a tube amp, which has been done, it's just a weird thing to do apart from experimenting. You cannot make a neutral tube amp though. You can make it more linear with negative feedback, but as you raise the amount of negative feedback you lower gain and thus headroom, and make clipping hard vs soft, so you start running into sound that's usually associated with solid state, apart from other problems such as stability. Hard clipping requires more wattage, obviously, which, again, is difficult to achieve with tubes. Some tube amps are more linear than others, though. But you cannot achieve the same precision as you can with SS. That's just the way it is, sorry.
Top end audiophile amps are just that
Well, no they aren't. And let's not dive into the audiophile mythology here please.
Also, hifi amps, tube or SS, do not use guitar speakers as load. This makes a huge difference because hifi speakers use mechanical damping, which makes an amplifier's job way easier in terms of linearity. Guitar speakers have loose suspension, are very efficient and you must have electrical ways of damping the resonance if you want linearity.
Try plugging that audiophile thingie into a guitar cabinet and see how linear it gets.