Curved? I am not sure understand what your visitor is suggesting. That looks like a nice, clean reveal. There are some shadows being thrown into the corners that make it look like the corners might not be perfectly aligned, but again, I think those are just photographic shadows. In the full view shot, it looks quite nice.

Fabricators, (maybe oldryder will chime in), typically go by the installation/template specs. If there isn't an installation reason for doing a square corner, the fabricator should have a discussion with you as to which way you would like it. Personally, I like to follow the contour of the sink. In your case, by the looks of it, that would be a slightly radius corner. I don't think the square corner is "wrong" per say. But again, I would always defer to the installation/template specs.

On a side note, if you haven't yet purchased a wire grid for the bottom of your sink, I would highly recommend it. Pots & pans are going to leave marks on that white sink.

I am a fabricator. Typically the sink cutout follows the sink shape. However, sharp inside corners are to be avoided because they create a "stress riser" in the countertop material that significantly increases the risk of a crack developing. Most quartz OEM's have a specific minimum for an inside corner radius for this reason. For my shop the min inside corner radius is 1/2". . If the customer insists we'll do a sharp inside corner but we will not warrant against cracking.

Additionally, the sink, as seen in the 2nd pic, doesn't seem to be properly aligned with the cutout. This may be an installation problem or a compromise by the installers to line the sink up as closely as they can with a cutout that is slightly incorrect. The relationship between the sink and the cutout should be consistent within 1/16" at all points. This is not difficult for a competent fabricator.

Thank you for your responses. And yes the sink doesn't look like it is aligned with the cutout.