ours are about a healthy 1/4", and about a 1/2" deeper. but we have 2 different sizes...larger ones in the window corners and smaller as moldding filler...we decided to use them and the corner blocks rather than making all the miter cuts.

There are two issues here: 1) poor workmanship, and the GC doesn't care. There are better materials for filling nail holes than caulk. And he's telling you this is how it is, and you can't do anything about it. 2) what is the price point of this new build? Does the price point of the new house actually pay the workers to do quality work? This is a legitimate question. Or has the majority of the profit already been squeezed out? It can be fixed. Not easily or inexpensively if it really is all the trim in the house and not only a few isolated sticks. Do you have any actual recourse with the builder to get this fixed?

If you use the same finish as the walls, the casings will disappear. What if you try painting the casings Alabaster but in a gloss finish? If that doesn’t work for you, maybe the darker color on the Alabaster strip, again in a gloss finish, would work. I think it will work just fine, What are you doing for window treatments? That, too, can make a difference. You leave the casings white, add draperies in an Alabaster tone so the fabric overlaps the white casing.

Again to be clear, I was the one who made the window and color scheme selections early-on as I had to choose a whole-house scheme in order to settle on frame/sash colors so that we could order windows. The "third" architect was/is an assistant to the one who designed our house and was my primary consultant in finalizing the siding and trim colors (and hence the original dilemma and possible rescue of the color scheme). I had no expectations of this house looking historic and would have considered a structure of this size and simple architecture to be boring and monolithic were it all the same color. Perhaps I should have asked for help at an earlier point than I did but I do not transfer "blame" (if the word even applies) to anyone else for however the color scheme turns out. If nothing else I can always return to my original plan of having different trim colors on the upper and lower levels, which I didn't think looked that bad. Here is a screenshot I was able to save of the front elevation with all-green trim: