I got an email from AdMob today saying:
Change to native ads policy: Native ads will require MediaView to render the video or main image asset. In a
If implementing Advanced Native Ads, use "imageScaleType" property of MediaView as suggested here in the official docs https://developers.google.com/admob/android/native/advanced#setting_imagescaletype
adView.mediaView.setImageScaleType(ImageView.ScaleType.CENTER_CROP)
or any other ScaleType as per requirement.