Plus, http, which this is based on, is an open and wide standard.
Apple is pointing out that the alternative - flash - is not as open, even if it's proprietary player is on more platforms.
I do find the reality distortion field that has people claiming adobe is more open than apple to be pretty powerful. Apples core technologies are generally open sourced, while I can't think of any open sourced adobe software.
Lack of wide support for a published standard doesn't have any bearing on its openness.