All undermount kitchen sinks, regardless of material used (metal, composite, cast iron, ceramic), are "sealed" to the countertop with silicone caulk and then "strapped" to the underside of the countertop. Any sink installed using only "epoxy" will fail. More important is your choice of the "reveal", I prefer the negative reveal...after 7 years no leaks or hidden crud.

I've installed several TZs over the years; no callbacks. Unlike conventional sinks, the TZs are adhered with a color matched methacrylate between the vertical flange and the vertical sink edges. I use the adjustments in the corners, then strap the sinks in place to get a perfect reveal.

"He explained that these sinks are installed using epoxy and also are sealed with epoxy. He said is not reliable and within 2 years the sink will drop, and the epoxy will have to be readded every 6 months."

Doesn't know of what he speaks.