It is a symmetric sphere where the Subdivisions determine the resolution of the polygons. While the default sphere is using Radial Segments and Rings. This difference is most notable in the high polygon count on the poles.
Move the extracted folder into the addons folder.
For this extension, I started by using godot-cpp-template.
https://schneide.blog/2016/07/15/generating-an-icosphere-in-c/ https://github.com/chateauferret for his improvement on the original addon.