They pay the big upcharge to reframe things. And they hire the GC that follows the designer’s design documents. Even if that includes the $$ change order to the customer.

It’s not easy to see what you’re describing in those photos. They’re very grainy. Sounds like you are working directly with plumbers? What kind of drawings are they working off of?

"They are installing most plumbing fixtures off center or in awkward locations because they say joists are in the way and that’s the only way they can do it. Is that true?"

No. Carpenters, not plumbers, can frame so the plumbers can place fixtures where they are supposed to go. These guys didn't put the money for any framing in their bid. Do not allow plumbers to cut wood, please.

The plumbers are doing what they can without the framing being changed. Joseph is right that you don't want plumbers cutting (butchering) wood, so if you want this done right you need to stop work until you can get a carpenter in who can accommodate what you want. This should have been thought out before, especially if you have an architect working with you.

I will also point out that you've got white PVC running horizontally and it looks like the joists have been compromised: one is completely cut away and the holes through the other two may have holes that exceed what the building code allows. Notching and boring

But I can't tell for sure about the holes because of the angle. In any case, if you are going to have tile on that wall, you want to insure sturdy framing as flexing can compromise the installation.

Are you working with a knowledgeable Designer or GC? Because none of that would fly in any of my job sites. Yes, reframing costs additional money. That is why you have a contingency budget on big projects like this.