I am not sure about this, but I think I have discovered the reason for the anomalies with the 5900 screenshots.
TW2003 was developed with a max frame buffer size of 128 MB for video cards. The first week of June, EA released a patch (1.2) that addresses users who have purchased 256 MB cards and the game not running properly.
I have since gone to the exact spot (10th green at Sahalee) and the water hazards (both of them) renders just fine on my Ti4600. I am pretty confident that if whoever took those screens will apply the patch, the 5900 should render the hazards properly.