It's better to spend the money now and know you did it right than having to go back and dig out around the house later because it is getting water into the basement.
As millions of people have found out!
It is better to try to route the water now than after all the bushes and the decks are in, making it very expensive and messy to fix later. Particularly since the basement walls, in this construction, are just floating on a bed of tamped crushed bluestone stone that could allow water to work its way back under the basement floor and up through cracks that will develop or around pipe riser openings. With classic construction the footers are dug into undisturbed soil and the french drain is laid on top of the shelf of the footer that extends out beyond the wall.
I would not allow them to run the spouting downspouts into the french drains, either, as is done by some builders to save a few bucks. That just results in quick flooding of the foundation area. The downspouts should be piped away from the house a good distance to an open-to-air outlet.
Washed river gravel is really your best bet for filling above the french drain. Any kind of crushed stone has sharp parallel edges and will compact or clog with clay. Look at what it does on a lane or driveway over time.
A 90 day theme sounds wonderful for a complete stick built house, but at this time of year I would be more concerned about them using anti-freeze in concrete, freezing temperatures during curing time, sun heat to seal down composition shingles, if that is what is being used, and other factors that could flaw the quality of construction.
How thick is the cement board used on the exterior of the walls? Is it a fiber cement?