The templates are just proposals for various ensembles. There are many other notation conventions like roman or arabic numbering, appearance of transpostions, different braces etc. etc, most of them can be adjusted in Layout/Notation Options.
You can
- create your own custom templates, Dorico provides both Horn and French Horn in the instrument list.
- set the language for instrument names in Preferences to German or Italian to get Horn/Corno even in a factory template.