At the end of the day, anyone can sue anyone (in the USA) over anything regardless if they have a case or not.
Likewise, speaking from experience, the line between published and unpublished for uses in copyright registration is very very nuanced. I have to assume the line between commercial and newsworthy is just as nuanced. Sure, there are definites, but most will fall into a grey area. A lawyer I hired in the beginning of the year for some legal issues made the comment that sometimes it all comes down to what the judge had for breakfast.
So, at the end of the day, having a signed release is always best.
Just to drive this point home, I went a lecture on the business of fine art by a successful NYC gallerist years ago. He told the story of the gallery of a friend showing the work of a photographer from who was in Europe in a NYC gallery. The photographer did not have any signed releases, but all the subjects where living in Europe, so no chance they would notice the show, right?. Plus typically shows in galleries are considered fair use anyway, so they did not think there would any chances of any legal issues. Or course the show needed to be advertised, and they picked the best image to do so. The person on the image they choose was vacationing in NYC when the show opened, and BAM, lawsuit followed.