Unfortunately I discovered this isn't the case. I contacted SmugMug support and they've already decided all Flickr users will be subject to SmugMug's policies as of May 25th. Existing Flickr content that satisfied Flickr's policies can be removed for SmugMug policy violations.

This is destructive and makes me sad for Flickr's future.

I just hope they don't decide to mass delete everything with a content filter applied, since in theory all that content violates their new policy.