Why can't I get the PostGIS version?

Question

PostgreSQL

Created a database with the template `postgis_22_sample`.
I do: `SELECT PostGIS_full_version();`
I get the result:
-----------------
ERROR: postgis_full_version() function does not exist
LINE 1: SELECT PostGIS_full_version();
^
HINT: No function found with the given name and argument types. Perhaps you should add explicit typecasts.
-----------------
I don't understand why? I see PostGIS extensions in extensions.