I'm not an EE so I'm not qualified to render any opinion from a technical standpoint.
Nor have I performed blind testing with my CJ Tube Amps vs solid state (only sighted comparisons, back in the day...though I've blind tested other audio gear in my home).
As a layman I can only sit back, watch the various debates between people who are more qualified, and infer what I can.
My inferences so far: There is nothing magical about tube amplification that, by default, makes any tube amp sound different from a well designed solid state amp. A competent amp designer can design a tube amp to sound indistinguishable from a solid state amp. (And, in Bob Carver's case, the reverse). Given this fact, and given we are often dealing with, in the big picture, quite subtle levels of distortion, it's likely that a decent portion of the "tube amp sounded different from SS amp" reports were due to expectations/biases etc, more than actual sonic differences.
On the other hand: It seems to me that a majority of those knowledgeable about amp building acknowledge that, yeah, tube amps have general liabilities vs solid state that, if you aren't really directing your energy at controlling them, it's easy enough to end up with a tube amp that audibly deviates from a solid state amp. Add to this the fact that, given the romantic notion many audiophiles and tube amp manufacturers have about tube amp sound, they essentially WANT a different sound from a tube amp vs a solid state amp. So given that tube amp manufacturers may be more in the "design by listening" group vs solid state, the fact they are seeking some different sound from solid state, and are using methods of evaluation and design that aren't being strictly guided by measurements, it's very plausible many of these tube amps end up reacting differently to a speaker load than a solid state amp, in an audible way. A fair amount of the Stereophile measurements of different tube amps seems to be evidence of this as well.
So, do my Conrad Johnson Premier 12 amps sound different than a competent transistor amp?
Certainly I very strongly perceive a difference whenever I tried going back to solid state - I heard the CJ as producing a slightly rounder, richer, slightly softened, fatter sound, with a slight upper midrange sort of "glow" or air. I prefer it every time next to an SS amp powering my speakers.
But to be consistent, I have to say: I don't know. That is, not with a scientific level of confidence controlled for bias. So I'd never make an objective claim about it.
Is it plausible I'm hearing sonic differences vs an SS amp? Given what I mentioned above, it seems plausible.
Also, adding to this, Archimago recently did a few posts assessing the results of testing for the audibility of types of harmonic distortion in listening to music:
http://archimago.blogspot.com/2020/06/blind-test-results-part-iii-is-high.html
In the comments I gave a link to measurements of the CJ amps and archimago agreed that it's highly plausible the amps are "flavoring" the sound.
So, I just sit back and try to balance everything I seem to have learned so far. The status of my belief is that, yes it's quite plausible my CJs sound different than the SS amps I've tried, and that I like the difference. But I can't know for sure without bind testing. However, at this point I have little urge to do the blind tests: I've already owned the amps for years, I like the sound of my system, and if my perception of their sound is some mixture of real and imagined (or just imagined), I'm ok with that. I also like tube amps conceptually and aesthetically: I like how my amps look, I like the design concept, I like the fact that when I'm looking at the glowing tubes I'm actually seeing the music signal in that glow. Etc.