Extension for New Embed Type Doesn't Show correctly in Lists widgets

I implemented a new Embed type to use in the TinyMCE editor to support our Communications group who wanted to assign a specific image as the Poster image for their videos. This was based on the conversation in this thread. https://community.telligent.com/community/10/f/ask-the-community/1145485/htmlsanitation-in-10-1. The extension works just as planned. It allows them to enter a URL to their video, a URL to their poster image and the size they want their video displayed. The output of the extension is the standard HTML5 <video> code using their poster image.

The one issue I have noted is that this embed extension is not displayed correctly when the item is displayed in the Activity Story Stream or the Blog - Post List widgets. The <video> and <source> tags have been scrubbed from the output, leaving only the alternative text that was inside the <video> tag for browsers that do not support HTML5 <video> tags. 

I also created what is essentially an identical extension for embedding <audio> into the TinyMCE. Same thing here. It displays fine in the post itself, but only shows the alternative text with the <audio> and <source> tags scrubbed from the output when it shows up in the Activity Story Stream or Blog - Post List widgets. 

Is there something I missed in the implementation? Or there something that needs to be done in those widgets? Or ...