Judging from the ratings your definitions have won. In my environment a Template is a _Course_, not a site, with no teaching content just some administrative content and formats, as in a MS Word dot file. (The 't' in dot is for template, I believe.) You call it the Shell. Your Template, a course with content, could be a Turn-key Course, for us.
Shell is out of bounds for us - too many IT folk: https://en.wikipedia.org/wiki/Shell_(computing).