WordPress will try to create a slug from the title. WordPress will al…

…so look for a corresponding page- template that matches the slug name. Therefore if a page template exists with the name page-no-title, WordPress will apply that template to any page with that unique slug. This causes unexpected template assigment. TT4 and TT5 most notably. It's also inconsistent since subsequent untitled pages created in the site editor will use the default template, slugs being unique. Anyway, let's just use WordPress's default behavior, which is to create a unique slug using wp_unique_post_slug if none exists.

packages/edit-site/src/components/add-new-post/index.js

@@ -45,7 +45,6 @@ export default function AddNewPostModal( { postType, onSave, onClose } ) {
 				{
 					status: 'draft',
 					title,
-					slug: title || __( 'No title' ),
 					content:
 						!! postTypeObject.template &&
 						postTypeObject.template.length