What problem does this address?

There are a couple of places where we refer to pages and posts when working with templates. A template can be used with a custom post type or multiple post types, so these messages can be confusing when a template is used, for example, for a product page or an email.

Examples

• a dialog when a user double-clicks a template block in template-lock mode.

• a description in the Templates panel in the Save Changes sidebar

This problem was also discussed in #67209

What is your proposed solution?

Option 1

We can avoid mentioning specific post types by making the messages more generic.
For example:
You’ve tried to select a block that is part of a template that may be used elsewhere on the site. Would you like to edit the template?
This change will affect other parts of your site that use this template.

Option 2

It is possible to associate a template with a custom post type or multiple post types via register_block_template and post_types. We could use this association, and in the messages, we could list labels of all post types associated with the template.

The post_types property is currently not available in the template data provided in the REST API. But there is a PR that exposes the property WordPress/wordpress-develop#7530. This PR seems to be a requirement for this second option to work.