The author remixed this model.
While this can be printed entirely out of TPU, it is optimised to be printed with the base and nozzle in a harder material, e.g. PLA or PETG. It has also been optimised to use less TPU at the bottom when simply slicing by layer, meaning you don't need a fancy multi-material printer to make it!
The bottom 1.6mm should be with the hard material, the next 35mm TPU, and the rest hard. A 3MF file has been included that simply uses a 35mm modifier box to change extruder at the right heights.