Drew–Johnson–Olesky–van den Driessche superpattern conjecture for sign patterns

A sign pattern is a matrix whose entries are $0$, $+$, or $-$. It is spectrally arbitrary if every monic real polynomial of degree $n$ is the characteristic polynomial of an $n\times n$ real matrix obtained by replacing its nonzero entries with real numbers of the corresponding signs. A sign pattern is a superpattern of another if it is obtained by replacing some of the latter's nonzero entries by arbitrary nonzero entries while retaining its existing nonzero entries; a spectrally arbitrary sign pattern is minimal if none of its proper subpatterns is spectrally arbitrary. Drew–Johnson–Olesky–van den Driessche's superpattern conjecture. If $S$ is a minimal spectrally arbitrary sign pattern, then any superpattern of $S$ is spectrally arbitrary. This conjecture asks whether spectral arbitrariness is preserved when additional nonzero entries are added to a minimal spectrally arbitrary sign pattern. The source states that it remained open before this paper, whose abstract claims to provide a counterexample, so the conjecture is refuted.