I made those models using a quiet impressive 3D Modeler for smartphones : Spacedraw. I worked for the sole coder of this app, an AI programmer, for about 3 years . Writing lengthy bug reports and improvement suggestions. Working without any compter 3D software was a real challenge, especially for the unwrapping that I had to do entirely by hand, more or less quad by quad.  I understood a lot, working with Spacedraw, about what’s behind the hood of our nowadays powerful tools.