Trying to use a custom element with createPortal() in a new documentPictureInPicture window is failing with an error.

React version: 19.1.0

Steps To Reproduce

1. Create a documentPictureInPicture window
2. Register custom element in new window
3. Render custom element in new window using createPortal()

Link to code example: https://codesandbox.io/p/sandbox/mystifying-mountain-h7gxtx

Note: I've created a similar sandbox but without react: https://codesandbox.io/p/sandbox/goofy-rumple-hk8lrs In this example there is a version that fails with the same error and a working solution (commented out):

// ⚠️ This fails with same error
const square = pipWindow.document.createElement("custom-square");
// ✅ This is successful
// const square = document.createElement("custom-square");

The current behavior

The custom element is not being created correctly and therefore not visible. The console in the documentPictureInPicture window shows the following error:

Uncaught NotSupportedError: Failed to execute 'createElement' on 'Document': The result must be in the same document
    at completeWork (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:11346:37)
    at runWithFiberInDEV (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:1519:30)
    at completeUnitOfWork (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:15268:19)
    at performUnitOfWork (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:15149:11)
    at workLoopSync (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:14956:41)
    at renderRootSync (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:14936:11)
    at performWorkOnRoot (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:14419:13)
    at performWorkOnRootViaSchedulerTask (https://h7gxtx.csb.app/node_modules/react-dom/cjs/react-dom-client.development.js:16216:7)
    at MessagePort.performWorkUntilDeadline (https://h7gxtx.csb.app/node_modules/scheduler/cjs/scheduler.development.js:45:48)

The expected behavior

The custom element being correctly created and rendered in the documentPictureInPicture window.