That's not supposed to happen. Let me check into it.
I'm not in control of the ad creative that Google serves users, rather I create the frame dimensions and the ads are supposed to stay within those frames. I have never enabled pop-up or full-page site ads.
EDIT: I have just checked on several Android phones and tablets - both logged in and unlogged - and I am not seeing any pop-up ads. I will have to explore further to see what might be going on. It might have something to do with Google services in the EU. Google has been making changes in order to stay compliant with EU requests, and it is a little more difficult for me to see what is going on because we don't get exactly the same service here in the US.