What are stereo screenshots for?
Stereo is, in short description, a name for 3D. It adds depth to the perception.
stereo 360 differs from the known 3D glasses by adding immersion. Any content shown with traditional 3D glasses will look really weird around the edges of the image. Stereo content viewed in a VR headset will surround the viewer in a much more consistent way.
You can read more about stereo 360 and its application in the link below:
https://bigmancgi.com/blog/mono-vs-stereo-vr/