It’s a browser support issue. You can conceivably write a converter for it. AFAIK not all video from iOS is .mov though. I’ve just tested a camera recording and it is a .mov whereas:
That file came from my iPhone and is mp4.
It comes down to this setting:
The high efficiency formats are heif for still images and heic for video in a .mov container.
@pmusaraj implemented a converter for the still images already over here.