@mr-smith It would be recommended to use Dynamic Media components (like Generic DM component, 360 Video, Interactive, Smart Crop, 3D) instead of directly adding the DM media url. You would also get other configuration options like selection of viewer, image/ viewer preset, modifiers, breakpoints, smart crop, etc.
The Scene7 Link which you have configured is an API link which will fetches the video based on best fit. For example if you're viewing the video in a mobile it will fetch its corresponding resolution rather than downloading a high resolution. Also, the video is generally downloaded in parts and not full at once based on scrubbing speed, buffer speed, etc. Once the video starts playing please observe the XHR entries in your browser network tab of type 'media'.