Sections of Submonoids of Nilpotent Groups

We show that every product of f.g.\ submonoids of a group G is a section of a f.g.\ submonoid of G×H₅(Z), where H₅(Z) is a Heisenberg group. This gives us a converse of a reduction of Bodart, and a new simple proof of the existence of a submonoid of a nilpotent group of class 2 with undecidable membership problem.