The Grundy domination number is not multiplicative on strong products

The strong product of the octahedron with a graph $H$ on $21$ vertices of Grundy domination number $10$ has Grundy domination number at least $21$. This disproves the conjecture of Brešar, Bujtás, Gologranc, Klavžar, Košmrlj, Patkós, Tuza and Vizer that \ggr(G\sprod H)=\ggr(G)\ggr(H) for all graphs $G$ and $H$.