Why didnt Genos' core fuse with its past version?


In One Punch Man manga chapter #168,

> Saitama returns to the past and fuses with his past self. His clothes also
> fuse, so the naked Saitama by fusing with the dressed Saitama appears with a
> suit which is half complete, with a hole in his private area. So if Saitama
> (human/organic) and clothes (inorganic) fuse with their former versions,

Why didnt Genos' core fuse with its past version?

