Your builder may strongly prefer that you not do that. Vegetation can take away work areas that they might use for storing supplies or working. Tools and supplies can usually be seen in an expanse of dirt but may never be found among wildflowers. Talk to your builder first and see where they may be OK with it and where not.

That's the kind of thing I was interested in knowing. Our builder tries to be very accommodating, and so I don't want to bring it up if it will be a PITA for the folks building the house.

The other concern is that a lot of "wildflower mixes" aren't really native, and some can be quite invasive.

Here is a link that might be useful: Possible concerns

I agree the builder won't "get it" and neither will the crews. There will be people worried about trampling them regardless of who you tell otherwise.

Also, I don't believe wildflowers are good mud control. I think grasses and ferns with deeper root structure.

Ask your contractor about mud control, I see sites with straw, wood chips etc. used for mud control and they can scoop and remove those later.

The wildflowers would not do much for either mud or erosion control because they take several months to get a decent root system.

For erosion control, you need "snakes" (those straw-filled tubes) going across slopes, and perhaps the sprayed-on chopped straw with biodegradable glue.

Be very careful of wildflower mixes. They contain a high percentage of noxious weeds. Trust me, I know. We spread a lot of supposedly high quality wildflower seed in the native areas around our house, and after 2 years we are still fighting a losing battle to get rid of them. Plain grass is far easier to deal with if you still think you need to plant something.