I tried to find it online but I’m not sure what section or key words to search for in the PDF I downloaded from the plumbing codes.

So who told you that you couldn't do that? Ask them for the actual code.

I have the whole story now...not sure how to explain it but it has a lot to do with how we had to build the structure since we’re in earthquake country. There are many competing factors: a tie down bracket, sheer wall, large/low window and a bolt into the concrete in the way of placing the sewer line centered on the sink window. Because of these structural limitations, and that code does not allow them to drill through the king studs they can’t run the drain line (and vent) close enough to the sink. There is something in the code that says you can’t have a bend in the line until the flood line of 36”...which is too close to the window and then the king studs get in the way anyway. I know nothing about the complexities of plumbing!

This makes more sense.

This is an engineered sheer wall and (I'm going to guess) it wasn't built with any extra space for plumbing.

So the complexity of this is waaay beyond this site. At the same time, you don't want your plumber designing your kitchen. Move this up-stream to someone who knows both the plumbing and structural codes and understands the impact on the design of the kitchen.

It’s basically going to make us move our cabinets out further from the wall to accommodate the plumbing and have deeper counters. We’re ok since we have the space. It’s stuff we don’t think about when we said ‘maximize the window’...I’d like a wall of windows...make the slider taller...and so on. They did tell us engineering-wise what those were going to cost/require, but then plumbing took the hit!

Put this back on "them". They don't design/engineer in a silo. They need to understand the ramifications all the way through. It's not your job to understand the intersection of those two codes, stop owning it. You paid someone to know this stuff.

Many want their kitchen sinks at a window. Often we have them in a 12" offset (window popped out from main wall), but if they are not, you might have to run the vent back into the cabinet space along the surface of the wall to get around the king studs. If you want the interior of your lower cabinet to look perfect, you have to move them out as you said, deepening the counter, or box around them with matching interior material.