https://webkit.org/blog/6784/new-video-policies-for-ios/:

• On iPhone, <video playsinline> elements will now be allowed to play inline, and will not automatically enter fullscreen mode when playback begins.
  <video> elements without playsinline attributes will continue to require fullscreen mode for playback on iPhone.

Might we worth to add the attribute by default. See the HTML playsinline attribute definition.