SYMPTOM:
When a Visual Insight dashboard is displayed inside of an iframe, enabling Presentation View allows the Strategy content to be displayed outside of the iframe instead of being contained inside it, in Strategy Web 9.3.1, like shown below.

In Presentation mode.

Notice how the content of the entire browser is occupied by the Visual Insight dashboard and the content of the HTML page outside the iframe is completely covered.
STEPS TO REPRODUCE:
CAUSE:
This is working as designed. In Strategy Web 9.3.1, presentation view is meant to cover up the entire browser window as in a "full screen" mode and this action takes place regardless of it being inside an iframe. An enhancement request has been logged for a non full screen mode type of presentation view.