• That Bicycling article is technically correct. But your application is inaccurate. Just read Bicycling's article about catching counterfeit carbon frames. That counterfeit frame article helps explain the vast (and costly) differences that the carbon and layup make in a bike's construction. The carbon and layup affect the weight, stiffness, and cost of a frameset. That is fact. Whether you value that difference is up to you, but it is fact.
• Giant is a popular US brand too. I have a Giant mountain bike. I have Pinarello road bike. I am not sure I get the point.
• You are not current about IAx vs IAxx performance. Read through threads here to catch up. The IAx has a taller head tube stack, and the Vision brake on the IAxx is very aero. Those offset some of the IAx's integrated bars and brakes.
• Tom Dumoulin on a Trinity is apples and peanut butter. His Trinity is UCI legal. Many of the fastest bikes are not UCI legal. The Cervelo P5 is one of the very few fast bikes that is also UCI legal.
• You may also want to catch up on aero benefits of BTA. Cervelo proved a while ago that a BTA bottle actually reduces drag, whereas the other vertical systems simply add less drag. So, if you wanted to improve the GTAP, you would probably want to think about getting the base Trinity Advanced model without integrated water and installing a BTA. But, this would take some wind tunnel work to confirm. So, I would just recommend a Felt IAx which is probably faster and the same price. Oh snap, Tom Dumoulin's bike does not have the integrated water or bento box...
  

Edit: Double-snap... Tom Dumoulin's bike was built on the Trinity Advanced Pro TT frameset. That is different from all their other bikes. Giant boasts a higher grade of carbon on that bike. I guess the better carbon mattered to Tom. That frameset alone is priced higher than the GTAP1 full bike. Hmmmm. Could it be that the GTAP line is basic carbon gimmicked-up with lots of plastic up front, and that is why they are cheaper and positioned alongside the Felt IAxx models in the market? The answer to that rhetorical question is "yes."