So I was doing some research, and I think the image of Lantana Man without the backpack wasn't recovered from Google's backend servers, but might have been recovered from Nancy's phone.
The reason I suspect this is if you look at the image, it is of lower quality (and smaller image size) in comparison to the still images from the Nest footage. If Nest sends push notifications with an image attached (which I believe it does), then the image could have shown up temporarily on Nancy's phone via notifications before it was overwritten a few hours later by other notifcations coming in on Nancy's phone. Because she didn't have a subscription, she wouldn't be able to check (or even be aware) what that notification was. However, because the image showed briefly on her phone as a thumbnail, it could have been saved--but in a place that she probably never looked, the cache. But someone with some technical knowledge would be able to find these thumbnails, and there might even be more of Lantana Man we didn't see.
Similiar methods have been done before. In the case of Cari Farver, LE was able to recover thumbnail images off of Liz Goylar's (her convicted murderer's) wiped SD card. One of the small thumbnail images appeared to be a part of Cari's body, and probably helped with Liz Goylar's conviction.
I wouldn't be surprised LE has more, but they are probably small 'thumbnail style' images from Nancy's notifications, similar to the one where he is without his backpack. They might have been holding back on sharing them because they would only be still images, with few identifying features. It was only when they were able to recover video from Google's backend they felt like they had enough to share. JMO.