Yes, it will make his life easier, but it will also make your house look better on the day it closes. There are about 15-20 trades that come into a new construction home after the painters have finished painting and not one of them will not do some kind of damage to the walls or trim. Carpet guys and flooring guys are the primary wall wreckers, but all the trades contribute.

Eggshell or any washable finish does not touch up nearly as well as flat. Dark colors are even worse and some brands just don't touch up well at all. Flat touches up great. Also, flat hides your drywall imperfections better so this is a plus for the builder as well. Also, most builders have a year end warranty program for drywall repairs, and after a year that eggshell is going to be even more difficult to touch up. Many recommend waiting until after the first year to start painting with your custom colors. Also, movers do damage, you don't know what colors you want until you furnish the home and hang window treatments, etc....really a whole lot of stuff to consider.

On the other side of the issue, some people just want the washable finish on the walls right away because the house is empty and they want the painting to be done so that they can just move in and live!

There are many good points on both sides really. You should expect a significant upgrade in the price of painting if you choose an eggshell finish. The flat paint is very cheap...eggshell is triple the price. Not only that, the labor time is more because eggshell is two coats usually over a primer and you will be cutting in all ceiling lines twice because the ceilings will stay flat. A normal 2500 square foot home for me usually costs about $1800 more to paint with eggshell and I'm the cheapest guy in town.