Why is a content type's node twig template being used by taxonomy term?
A view can show content or fields. The taxonomy term view shows content and this means it renders each node in a node template. If you don't want that the template of the full node display is picked up by the view use different view modes, which you can append to the template name:

node--course--full.html twig
node--course--teaser.html.twig


teaser is the view mode the taxonomy term view uses by default. You can change this to a custom view mode if you want to style the nodes displayed here in a different way than in the front page view which uses teaser as well.