Hi,
I picked this up today.
If you add a plugin in the normal way shown below, the button shows in flash but not in html5. This works as expected.
The problem is that if you add the plugin via the addplugin() method shown below then it still works in flash, but it also shows in html5. In this case Html5 does not pick up the devices attribute.
Code
<action name="create_image">
addplugin(the_image);
set(plugin[the_image].devices,flash);
set(plugin[the_image].url, "random_image.jpg");
</action>
Note: Flash respects the devices attribute in with methods, but html5 does not.