As others stated, this demo dataset is pretty simple. I believe it's only using Natural Earth data (https://www.naturalearthdata.com/). The primary focus is on the rendering library.
Sorry :p It’s ironic because I had a friend once—well we shared kitchen and bathroom in the student housing, flatmates of sorts—that used to refer to Google Maps as “Google Map” and I never corrected her because I just found that adorable for whatever reason. Lol.
The SDK is just a library, used to render vector map tiles, usually in the MVT-format: https://docs.mapbox.com/vector-tiles/specification/
Most maps rendered with such an SDK are based on OpenStreetMap data.