Thanks for the report! The Foxfooding doc is incorrect and needs to be updated. In the new design, the text for "Watch in Picture-in-Picture" only displays for the first time a user engages with the button. This is to help introduce users to the feature. After that you will only see the small circular icon that you see in the screenshot, no text is shown on hover. Since this is the expected behaviour, I'm going to close this report as invalid.
Bug 1667239 Comment 7 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Thanks for the report! The Foxfooding doc is missing some information and needs to be updated. In the new design, the text for "Watch in Picture-in-Picture" only displays for the first time a user engages with the button. This is to help introduce users to the feature. After that you will only see the small circular icon that you see in the screenshot, no text is shown on hover. Since this is the expected behaviour, I'm going to close this report as invalid.