The filename single-recipe.php is telling WordPress “only use this file to display single ‘recipe’ CPT posts.”
If you want to use it as a Page template, you can either rename the file tpl-recipe.php (or something similar, it doesn’t have to be this filename, it just has to not be a recognized pattern like single-cptslug.php) – in which case you’ll have to manually choose that template every time you create a new Recipe –
Or, you can have two files. One named single-recipe.php which does NOT have the comments at the top, and one named tpl-recipe.php (or similar) which DOES have the comments at the top.