Your documentation says any theme content can be installed to any other theme. I installed the Boxed theme and wanted to install some content from the Basic theme to it. But when you go to Appearance->Import Demo Data
the Basic theme is not there to import from (all the other themes are). Please tell me how I can install some of the demo content from the Basic theme to other themes?
I hope you are well today and thank you for your question.
Currently due to some limitation you can install Basic demo content only from Legacy demo installation method from Tools -> Demo Content Install but please note that Legacy method replaces all your existing site content with demo content.