Hello,
You are using a youtube video, Youtube haven't yet released their html5 api, so when you are using a pure htlm5 devices such as iOS with youtube, then jwplayer use a craft fallback mechanism :
"For YouTube streams, the plain YouTube <embed> code is inserted. This triggers a special-case embed of the YouTube player on iOS and Android devices. Videos will simply play inline, but the JW Player interface and API are not available."
So this come from how youtube display it not jwplayer.