Weak Roberson Conjecture on non-isomorphic homomorphism indistinguishability

Let $\mathcal{F}$ be a class of graphs, and let $\equiv_{\mathcal{F}}$ denote the relation on graphs defined by equality of homomorphism counts from every graph in $\mathcal{F}$. A graph class is minor closed if it contains every minor of each of its graphs, and it is closed under disjoint unions if the disjoint union of any two members belongs to the class. Weak Roberson Conjecture. Every class of graphs that is minor closed, closed under disjoint unions, and is not the class of all graphs has a homomorphism indistinguishability relation that is not equal to isomorphism. This weaker conjecture would still imply that every proper minor-closed, disjoint-union-closed class fails to distinguish all non-isomorphic graphs by homomorphism counts, and it remains open according to the supplied source context.