I've done a lot of kitchens over the years. I used to fabricate and install formica and corian tops. It was always considered unacceptable to put a seam in the middle of a sink or cooktop. As time goes on, workmanship continues to slide. In this case there wasn't even a real need to put the seams there.
The installer claims that the bar sink is crooked because he wasn't supplied the paper template. He only took the sink back to the shop with him for the hole. I just had to laugh. If he can't cut the hole square with the sink, I don't think a paper template would have helped.
I'll search some more but if you don't know of a standard, then there probably isn't one. Thanks Jerry.

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