Well we have built several decks with this material on the river and it has not warped and cracked. The deck in the first picture was built in 2001. It has withstood many strong storms and humidity. It's still just as solid as it was when it was built. The client is still very happy with it.
As far as using higher end wood for the decking, this is what the client wanted. We have another deck to build right behind this one for the neighbor. They are wanting more higher end style.
I assure you it is structurally sound. Our company owner and designer for the project started in construction in Los Angeles California. I'm sure you realize California has some of the toughest building codes in the country. There are no requirements for an engineering stamp in the state of Missouri. That's very unfortunate for our state because ANYBODY can call themselves a contractor. We get so many calls to fix work that others have done incorrectly. There are not even licensing requirements for building inspectors.
We also use a marine grade plywood to protect it from humidity to keep it from buckling.