I take it you’re referring to Lite Mode Maps
If you don’t see the lightening bolt icon in Full Maps, you can force it to switch to Lite Mode maps.
• Open Maps
• Add the following text to the URL and hit Enter
I don’t know what the dates in Maps & SU Location Snapshot actually mean.
My guess is they’re nothing more than copyright boilerplate.
As for the source of the image, your guess is as good as mine.
The SU Location Snapshot image is same image as in Lite Mode Maps.
Lite Mode Maps displays the following image info:
Map data ©2016 Google Imagery ©2016 , DigitalGlobe, U.S. Geological Survey, USDA Farm Service Agency
While the info displayed in the SU Snapshot is different.
When I exported today’s Location Snapshot from SU, the image properties merely yield today’s date.
But as you can see, it’s the same image as in GE today.
GE clearly states the Imagery Date 6/26/2016.
To me, it seems the only way to know which image is most up to date is via GE and/or ‘local knowledge’
SU Location Snapshot
Maps Lite Mode