Painted or primed? What type of construction is tis, tract or developer? It would get touched up by your getting it matched by the paint store and hoping quite honestly.

They said painted. I’ve never heard of this. I’ve only heard of primed and it’s a factory white color. Custom home builder

You must ask them to clarify what you are getting in every regard. There will be joins in trim , miters at crown molding. We have no clue the size of your trim, the LOOK of your trim, a door style, paneled, how many panels, shaker ? Other? A single panel?

Also..please define "custom" ? Luxury build, design build, or custom as you get to select from a few options in any category from the builder?

All trim would need finish nails covered, painted , and you need caulk. NO trim is install and walk away.

My guess is yours may be as common as something picked up at Home Depot

5 1/2 square trim, 3 1/2 casing and 4 1/2 header with reveal. -3 panel shaker doors. I did ask I was told solid wood poplar doors and trim.
Custom design build with some options, allowances.

Casing style & trim

"Custom design build with some options, allowances."

Make that one of the options than and tell them you do not want them prepainted OR that they need to tell you the paint color and give you some for touch ups.

Is there another house, he has done, where you can go check out the prefinished trim? If so, I would go do that, before you order it. Since all trim needs touch ups after it is put up in place, and nail holes filled etc, I would want to know just how they do all that. Also, is it satin finish, or semi gloss finish, and what had you intended for the finish.

What is your paint "schedule" ( the list, not the timing )

What are trim WHITE options?

What is the wall paint protocol? Primer and one coat? Or primer and two coats?

What paint finish for walls and what paint finish for trim?

What is the limit on number of wall colors?

That alone, all those questions, will tell you how "custom" your custom actually is.

"They said painted. I’ve never heard of this. I’ve only heard of primed and it’s a factory white color."

I installed Belldinni Optima solid core, interior doors. The doors and trim were painted by the factory. The finish is perfectly-smooth, satin white, and does not look "plasticky" or cheap. The jams included weatherstripping (unusual for an interior door) that covered the screws (nails were not used) so no touch-ups were required. The paint color is slightly grayer than the surrounding walls -- painted Behr Ultra Pure White -- but still look great.

I'd suggest getting a paint sample (e.g., an actual piece of finished trim) so you can assess the color and texture, and select an appropriate wall paint.

Look at what Jan posted that Home Depot sells (or other big box stores). This stuff is milled like crap! The finish is crap - it's either "wrapped" with contact paper and called "pre-finished", or it's sprayed with garbage paint. NOT at all smooth!

We considered moving, and toured a few new build homes in the 1.5 - 2 million dollar range. We were appalled at how bad the finishes were!

We have friends who just finished a new build (5 million - not including the exterior landscaping), and even their paint finishes were unimpressive.

There are upper end companies offering pre-finished doors, but if that was the case, your builder would tell you the brand.