"without using any assets" vs "relying on no external assets" but it's not my area so I may be misunderstanding.
"Ours is entirely procedural" == ""Infinigen is entirely procedural"
"relying on no external assets" == "every asset, from shape to texture, is generated from scratch via randomized mathematical rules, using no external source"
If that doesn't make it make it clear, could you elaborate on the part that doesn't click and I'll try and explain further.