It seems you're right. Support of <iframe> in iOS is lacking, due to limitations imposed mostly by the PhoneGap/Cordova library on which our native mobile client is based. In fact in a newer version of the library, included in our latest version (2.1.15 at the moment), the <iframe> content is not displayed at all, not even in a separate browser.
We shall investigate it further, but I do not expect this issue to be resolved any time soon, sorry.
For best results, use the Firefox browser..