Apple has documented a unique behavior in this particular document that is definitely worth exploring. The information provided covers various aspects related to video usage on the iPad, shedding light on important considerations.
Link to Apple's documentation for further insights
A Closer Look at Default Height and Width Settings on iOS
iOS devices allocate a default height and width of 150 x 300 while displaying videos until the movie metadata fully loads as actual dimensions are unknown beforehand. It's crucial to define your preferred height and width attributes to ensure an optimal user experience on iOS devices, particularly on iPads where video playback is confined within the designated space.
Additionally, you may find this related question intriguing:
Exploring why Safari on iPad (iOS6) fails to scale HTML5 videos to occupy entire page width