On the face of it, you don’t have any saved layout options for part layouts. Could you please try quitting Dorico, and temporarily moving the file layoutoptions_scores.xml out of %APPDATA%\Steinberg\Dorico 4? Then restart Dorico and see whether you get the same unexpected behaviour.
I tried a lot of templates. Except for the empty template, everything looks fine.
I have a few other problems like Trumpet in B flat missing (German Version). I updated Dorico since Version 1 with every new update. Perhaps it would be advisable to bring Dorico into a fresh state?!?
Your most recent reply helped me to understand your initial post more clearly. You are talking about specifically creating a project template from the Empty choice in the Hub, and the part layouts that get created when you start adding players to such a project. I can see the behaviour you describe, and we’ll adjust this in future versions.