  The semigroup inclusion class $\mathbf{I} = [xyxy = xy; xyz \in \{xywz,
xuyz\}]$ is the union of two maximal subvarieties of $\mathbf{GRB} =
[xyzxy=xy]$. Monzo ( arXiv:1411.4860 ) described the lattice of semigroup
inclusion classes below $\mathbf{I}$ and asked if $\mathbf{I}$ is covered by
$\mathbf{GRB}$. Our main result is a characterization of $\mathbf{I}$ which
makes it easy to answer Monzo's question in the negative.
