I have talked and talked to the kitchen designer and he insists that this what they do most of and get least complaints about. He really does not want to do anythingcelse.

Im with you. I think the neutral is vey hard for them to do is part of it.

That said, the silucone on positive a b d neutral does get tired looking after being scrubbed for a couple of years, probably stains too.

Tgey all have drawbacks.

Makes me wonder if drop is is really all that bad

The illustration above is slightly deceptive. Undermount sinks do not have a perfect 90 degree edge at the flange, nor is the stone sharp on the bottom edge. Because the sink edge is slightly rounded, not square as illustrated, a flush reveal creates an elongated silicone joint which starts to fray, becomes black, contaminated, and unsanitary:

A negative reveal creates a "crud ledge" which is difficult to clean (unless out of sight, out of mind works for you) and offers the bottom of the exposed edge no protection from chipping.

A slight positive reveal makes a perfect tight seal between the bottom edge of the stone, protecting it; a crud ledge and an elongated silicone joint are impossible. You can see and access it for easy cleaning and nothing "gets on it and stays dirty":

Fabricators love the negative reveal because if the sink is off a poo, no one knows.

If I replace your sink, you're getting a slight positive reveal or you'll get your deposit back. It's your sink and you're paying, but my name is on it and my name doesn't go on chipping, fraying, black, and unsanitary.

"It's been quite a few years and has dropped down some."

This is not only unsanitary, but a leaking sink puts most reinforcement steel in mortal and catastrophic danger. Your edge will literally jump off the countertop on to the floor when the leak seeps past the polyester the cold steel rod is improperly imbeded in, oxidizes, expands, and splits the stone. Google www.ihatemysink.com, "Just Ask Joe", and "Curing Countertop Cancer" please (sorry my link's not working) for the gory details.

If you see black/brown crud at your undermount sink, it's leaking and cannot be fixed topically. The sink must be dropped, the flange and stone bottom cleaned, the flange siliconed, and the sink strapped, not clipped or blocked, back in place. This takes little over an hour, but we are really good at it because we've done this hundreds of times.

This is what that leaker looks like when you drop it:

You ain't cleanin' that with no damn toothbrush standin' at the sink.

"That said, the silucone on positive a b d neutral does get tired looking after being scrubbed for a couple of years, probably stains too."

There is nothing exposed to get "tired looking" on a sink with a slight positive reveal. Virually no silicone is exposed; nothing to maintain or recaulk ever. No stains.

I've never had this callback in over 4 years; if it happened, I should have by now.