thats good. who paid for the inspector?

What's going on underneath? Basement? Damp, musty? Crawlspace? Heavy rain tells me it could be a drainage issue around the house or maybe a sloped hill that's driving the runoff to the wrong place. Just guessing on that part

Crawlspaces require SPECIFIC venting/cross venting and a vapour barrier over the raw earth. The HVAC not running sounds like the culprit. This is a builder's Oopsa.

The center of the planks will tell you the DIRECTION of the moisture. If the center of the plank is sitting LOWER than the edges (like yours are = "cupping") then the centre is pointing DOWN....That means the BOTTOM of the planks are WETTER than the top of the planks. Just like yours are showing. That indicates that something BELOW the plank is causing issues with the wood. And that often comes from what it is SITTING on...like damp plywood that was never acclimated/dried properly before install (ahem....HVAC needs to be on and at living conditions for plywood to become "dry enough").

IS the HVAC running yet???? Do you have a humidistat added to your HVAC?

It is *possible this can be corrected - over time - by EXTREME regulation of indoor living conditions. But it be prepared that even THAT won't help. Sadly wood GRABS moisture MUCH MUCH faster than it lets it go. So it may only take 3 weeks for wood to grab all that unconditioned moisture (no HVAC, no dehumidifier, no A/C, etc), but it could take MONTHS to let go and settle down. And you will never know if it works until many many months have passed.

Wait for the Inspector to give you some hints and tips. But the builder made a massive mistake by installing hardwoods in an unconditioned space. Massive, massive mistake. That is flooring installing 101. A decent flooring installer would have told the builder to "call me when the HVAC is in" and would have walked away (which is why builders don't like using these "decent" guys - they have too much knowledge).

Keep us posted on the Inspector's report.

Cupping usually means a difference in moisture/humidity between above and below the flooring; create conditions whereby the dehumidified air space above is drier than anything below, and the boards will cup. I witnessed a flooring contractor (not me) install a prefinished hardwood floor below grade in a church. There was no attempt to vapor proof the concrete slab. Consequently the floor undergoes changes when the moisture from below increases and the moisture in the occupied space becomes drier. Good luck with the NWFA inspector you have coming. He or she ought to be able to diagnose the cause of your issue.

And as gregmills has advised, don't sign any papers until you are thoroughly satisfied that the problem is resolved.

Any update on the report?