  This technical note addresses an issue [arXiv:2310.14683] with the proof (but
not the statement) of [arXiv:2003.05030, Proposition 4]. The statement of the
proposition is correct, but the proof as written in [arXiv:2003.05030] is not
and due to a typo in the manuscript, a reference to the correct proof is
effectively missing. In the sequel, we present [arXiv:2003.05030, Proposition
4] and its proof. The proof follows from results in [2] that we reproduce here
for clarity of exposition.
  Since the statement of the proposition remains correct, no change in the
results of [arXiv:2003.05030] are required. In particular, Lemma 3 and Lemma 4
showing spectral convergence of graphs to graphons, Theorem 1 showing
convergence of the GFT to the WFT, and Theorems 3 and 4 showing convergence of
graph to graphon filters, remain valid.
