Actually with Cornerstone it's such old code it's actually using a
<frameset> rather than an
<iframe>...! Causes much the same problems with Safari though.
No, I know of no other workaround aside from using the launchNewWindow extension. You only need to configure it to activate for iOS though.
And yes, SCORM Cloud doesn't use either
<frameset> or an
<iframe> which is why it all works fine there.