Graphs 2 and 6 (of the 12 candidate minimal 13-vertex graphs from c993833c) are UNCONDITIONALLY non-realisable in R^4, certified two independent exact ways: (A) the Groebner basis of the rigid-frame edge ideal over QQ equals [1], so the complex variety is empty (a fortiori no real realisation); (B) an elementary rigid-frame propagation (multilateration cascade) closes every branch of a finite search tree in exact rational arithmetic. For both graphs the cascade forces two facet-reflection points and then a third vertex whose five unit-distance equations have no real solution.