there are lots of bonding agents and epoxies out there that are not urushi based , actually food safe, and just as easily doused in gold dust, and completely compatible with prepared ceramics.
I will not fault anyone for not believing the certification, but I would personally want to see a more authoritative source than an undated ceramics FAQ. But this is just personal style! Being suspicious of regulatory thresholds is prudent.
(And this FAQ has me wanting to revisit my priors and research this a little more specifically, because its assertions are plausible, but need sources or explanations or dates, for cross-checking. Food-grade epoxy I believe in would be a handy thing to have exist; I do have some certified food grade epoxy in my garage that I haven’t used for anything yet and I’d dislike downgrading it to just “epoxy.”)