I have actually seen Stardock do a lot of work towards supporting insider builds of Windows 11. A lot of the fixes that comes with later releases of products do have notes that fixes the functionality of an insider build.
The reason they state that they do not support insider builds is for 2 reasons. One Windows does not announce what they release on these builds ahead of time and therefore breaks all kinds of functionality without warning to third party software companies. And 2, functionality of released versions of products always takes priority.
Therefore, Stardock does actually support insider builds to a degree but has to add a disclaimer that they do not so people don't get upset that their stuff isn't working yet.