From what I have heard the issue for video games is that, from a legal perspective, they are seen as "toys" (regardless of age restrictions for specific games.)
The distribution of Nazi-symbolism (as well as all proganda from/for forbidden parties) is outlawed in Germany with a few exceptions:
1. if they are part of citizen education to protect against anticonstitutional endeavors.
2. if they are part of art or science
3. if they are part of research and teaching
4. if they are part of reports on events and process of historic and current affairs
The prevailing law theory in Germany still constitutes tha video games are lawfully not "categorised" as art, neither do they report on events of historic affairs. Some "classify" (=define!) them as toys in Germany which makes a lot of sense. They are not purely entertainment like a movie, they have an inherent interactional character and offer the user certain ways of dealing with them. Video games have more in common with toys than movies, that is pretty easy to accept. The idea of protection with the law is that (Nazi)-propagandists can't make games to glorify their symbolism and distribute them on school yards etc. There are constant discussions in the law scene to classify video games as a form of art, though. Of course, those processes last a looooong time.
However, there has been a lot of misunderstanding of German laws in the gaming industry! The is no lawful definition of video games being toys. According to German law, each and every case (=game) has to be scrutinized individually. Until today, there has only been 1 ruling of a German law court regarding Nazi-symbolism in a video game and that case was 21 years ago and was concerned with the first Wolfenstein 3D.
So there is a pretty good chance if a game nowadays featured a swastika it would not be forbidden by a court because the perception of video games has changed. (HoI, being the sandbox game it is and the level of freedom it provides the user with, it might be tricky). No publisher dares to actually try it out though, for one simple reason: the German USK (a self-monitoring of entertainment software, somewhat comparable to PEGI) will not rate any games with swastikas in it for inexplicable (and intransparant) reasons. A game without USK seal is very hard to sell in Germany as it can be indexed by the government at any time. A consequent trial, that may exculpates the publisher would take months or years and the game could not be sold. This is economically bullshit. So the gaming companies just go the easy way (understandably!) and create a censored version and blame the German law, because the law can't speak up and defend itself. This will go on until legal certainty will be established, which won't be the case until someone goes on trial. Vicious circle...
I hope that this will not be so since it would make quite a few German HOI Players skip HOI4 (at least those who I know).
So they only want to play the game if they get swastikas, Hitlers and Görings? That is kind of twisted, don't you think?