thanks! i was wondering if that was the case, but then i found this:
https://support.google.com/dfp_premium/answer/6366910?hl=en which mentions its an option for custom rendering. I initially built the app with the systed defined format and the GADNativeContentAdView, but the problem was, the default behavior kicks the user out of the app, which is not the experience we were hoping for. We wanted to build a native experience where ads are displayed and viewed in the app. Is that possible to do and still receive backfill ads? thanks again, this is really helping us