EDIT:
So according to this thread, this is a Google related change and not Nvidia?
In which case, similar to the banner issue from a previous update, you can get a different launcher (see comments for FLauncher) to avoid it
https://www.reddit.com/r/ShieldAndroidTV/comments/181vh4t/ads_at_full_screen/
Would I need to side load this on shield?
You can follow the documentation on the git repo, where both methods are described.
https://gitlab.com/flauncher/flauncher#set-flauncher-as-default-launcher