It's actually not just a technicality. National Socialists really were socialists - not only in name. They apparently took the 'Nationalism' more seriously than the 'Socialism', but they were, nonetheless, actual socialists.
For example, in Hitler's Germany, all German citizens were guaranteed a job by the government. All German citizens were entitled to an education at government expense. Healthcare was not totally socialized, but was heavily subsidized by the government. Etc., etc., etc. Sounds reasonably socialist to me.
I agree with you, but on the other hand, that also makes folks like Henry Ford socialist.
Back in the 20s, Ford's workers also enjoyed many of the things commonly associated with socialism: Free daycare, subsidised housing, free medical care, recreation & sports complexes, etc.
And he was quite fond of the Nazis, and they were equally impressed by him - Goebbels translated Ford's antisemetic newspaper & used chunks of it in his speeches, verbatim

I guess the man who epitomises capitalist industrialism is a closet socialist

I was not implying any kind of value judgement at all - just relating historical fact.
EDIT: I realized I did not answer your point. It is a fact that capitalists can practice a little socialism, socialists can practice a little capitalism, and either can be practiced to varying degrees by both good and evil men. We do not live in a binary universe.
Your edit is pretty much what I was trying to say. There is nothing inherently wrong with Socialism. The Reich's (amazing) initial success in WW2 was, in large part, due to its socialist aspects: state taking control of the industry, subsidized scientific research, etc., etc. It's the "Nationalist" part that made nazis ...unlovable. The whole racial purity, eugenics, antisemitism, lebensraum at any cost etc. The "socialism" part worked like a charm

Many would agree that Henry Ford was a fascist/socialist. He came up with a great idea, implemented brilliantly bringing the Model T which was ahead of its time. He also invented the production line which was also brilliant. I grew up admiring Henry Ford for those very things. Upon further research I found that his socialist/fascist tendencies tended to get in the way of being competitive moving forward. He just wanted to keep churning out Model Ts forever with the focus on making more, cheaper. He did not, however, focus on improving his design. Competitors caught up and surpassed his original vehicle and his son had to fight to push new model vehicles out to keep up. His father just focused on building larger factories and pushing out more Model Ts. Converting those large factories for military vehicles is probably what saved the company from bankruptcy.
As for Hitler, I will admit that I just threw him out because he was a member of the National Socialist party, not because I believe he was some huge bastion of socialism like Mussolini. But socialists (I will avoid saying communists because I know you prefer the term progressive or socialist these days) tend to blame the leaders who gain power in such regimes only to "not implement socialism right".
But, like I tell my conservative friends who complain about welfare programs, you gave them the power. Your system helped to grow the government to the point that they can do whatever they want. If a thief robs you and spends your money on drugs you shouldn't be upset that he spent the money on drugs and go on a tirade about how he should have used the money for food. He took your money.
Socialism takes power from the people. Those that believe in the ideal might think that the perfect system would then be to distribute that power equally among all of the people. But guess what? Too late. They took the power. They could give a rats ass about what system gave them that power or what they promised to do with it. It is now their power and they can do whatever they want with it because you were too stupid to protect that power. So socialism is the best breeding ground for people like Hitler, Stalin, Mao, Che, Mussolini, Bush, Obama, Clinton etc. They will take your power and do whatever they want with it.