Data-src instead of src in video tag

I’m wondering why the video tag for video brics is data-src instead of src. Here’s how I usually make video tags when I’m hand coding them:

<;video autoplay=‘true’ loop=‘true’ preload playsinline=‘true’ poster=’’ class=‘video landscape desktop
src=’“filename.mp4” type=‘video/mp4’ ;/video>

The video bric uses data-src. But I look in the generated javascript and there’s no reference to it. I want to be able to alter it using my own custom js. Is there some custom javascript that is handling the video?