But they're not dealing with same-name conflicts, they specifically said
And they clearly show 2 blocks, the modified primitive, and the custom block, which is a different name than the primitive.
Furthermore, what does this have to do with metaprogramming? They're editing the blocks manually, and they're also just using a custom block to house the original primitive function, exactly the same thing you do with the embroidery library. The only difference is that they're duplicating the original block, rather than manually creating the custom block.
They're just explaining how after duplicating the primitive block and editing the new custom block, the custom block will be replaced with an undefined block, and the primitive will be replaced with the modifications you did to the custom block. I was able to reproduce what they're doing without renaming the primitive.
I did also test to see if it was the selector of the duplicated block that was the issue, but it doesn't seem to be, which further emphasizes that this is not a same-name conflict.