[scoped-custom-element-registry] When used, elements defined globally remain undefined

[tpluscode]

Description

In short, I wanted to use globally defined elements in an element which also uses a scoped registry. In my real scenario, the global elements are Shoelace.

Unfortunately, if I use a global element inside a shadow root with scoped registry, it is not created as expected.

Example

https://lit.dev/playground/#gist=aeaab7d7ae68b4341eee63c47d663337

Steps to reproduce

1. Define my-parent with a scoped custom element registry
2. In its shadow DOM render a my-child element
3. Define my-child in global registry

Expected behavior

my-child should be correctly upgraded

Actual behavior

my-child remains undefined unless it is added to the scoped element registry

Version

"@webcomponents/scoped-custom-element-registry": "^0.0.9",
"@open-wc/scoped-elements": "^3.0.5",