Update: the company came out today to repair the seam. It looks exactly the same as before. They are blaming it on our cabinets not being level, which is was not the case. The installer said they do not use gorilla grips, only repaired seam by hand. I mentioned the epoxy being too light, however, seam looks exactly as it did before. I don't really know what my options are at this point.

located right in the moddle of the counter. and where were the papers you signed off on to show where the pieces were going to be placed/cut? (how about showing us the entire countertop?) The fabricator (or someone) should have showed you were the seams were going to be located. What is your countertop? Black forest? it's very pretty. why not get a nice display item like these cannisters and wood cutting boards and place it at the seam. it will draw the eye up and away. Honed Black Forest. is this yours? They did a great job on the vein matchup. Would you like to see a really bad seam matchup?

What’s a 0-radius corner? It's another term for an internal corner that is a sharp 90-degree angle, i.e. there is no curve to it. The sharp 90-degree angle can be more prone to chips and cracks is my understanding, but I am not a Pro. Perhaps one of the Pro counter people like @joseph_corlett will chime in. Edited to add a couple pics of sinks with more rounded corners to illustrate. Many people like the look of sharp 90-degree corners, but it may mean more of risk of chipping like I mentioned.

The only construction material that people seem to expect to look carved out of one giant block of material is kitchen countertops, and this was something that is promoted by the industry itself. I am not sure why this one thing is supposed to look seamless. I've seen pictures where I think the rest of the installation quality is pretty meh, but the question is about the seam and they don't seem to notice the rest. It's a good seam. It's not invisible, and the seams of this sort of material can't be matched unless it is book matched slabs instead of standard slabs.