Path detection won't work on aliases

if you assign a custom breadcrumb (call it custom breadcrumb A) to the path node-16-alias you should get the custom breadcrumb when the url is .../node-16-alias . You can set up a different custom breadcrumb (custom breadcrumb B) and assign it to the path node/16. When you visit the page via the url .../node/16 you would get custom breadcrumb B instead.

The breadcrumb depends on the path taken to get to the page. The two paths node/16 and node-16-alias are different paths, so you will not get the same custom_breadcrumb_paths on both of those pages unless you define two custom breadcrumbs.

At the moment, this is by design. But it would be straightforward to include (as a new feature) an option to assign the custom_breadcrumbs_path breadcrumb to the normal path and any aliases.

See also #850268: custom_breadcrumbs_paths distinguishes between node/NID and path alias