16% in all wood , or different in areas , wood take a Long time to dry
when wet, new and green. House is not heated or dehumidified. I have a
good Delmhorst Moisture meter, it took a frame sill 1 yr to dry after
being soaked. It measured maybe 15% after the leak was fixed 6 months
later. Today years later it is 0% 1%, a humid basement.
Jack a house you are kidding , you dont even know its bad. Its not
even your house.

French drain probably necessary . French drains usualy use pumps.

Its their house , they can see the floor and leaks , it passed
inspection Right. So you are going to new home owners scaring the ****
out of them and being a nosy body telling people their new floors are
bad , that Somebody may have heard their foundation Crack in the Real
cold winter , when you suspect they did it wrong anyway. and their
foundation may fail their house is on a lake and full of extremely high
wood moisture. Its a good thing you werent allowed in the house while
it was being built, you would condem the whole place

Did you ever stop to think it aint your business, it may be normal, and
you are an intrusive , disruptive pest ruining peoples privacy and new
home and scaring the **** out of them. What you hate the builder ?
this is your revenge. You should worry about your life and house not
people that you dont know or didnt ask for your two cents worth of
doughtfull fears.