After writing a .NET program that takes an image capture and generates a palette file for use with software emulators, such as FCEUX, I confirmed that the PEXHDCAP (with its RGB 4:4:4 to YUV 4:2:2 color space conversion) is unsuitable for accurate image analysis and palette file generation. RGB 4:4:4 to YUV 4:2:2 color space conversion (includes chroma subsampling) is found on virtually all HDMI capture cards on the market including the Elgato solutions that are popular with the streaming crowd.
After searching for an affordable solution I discovered that the latest Black Magic Designs Intensity Pro 4K supported uncompressed RGB 4:4:4 HDMI input at 1080p60! After having troubles with their original card, the Intensity Pro (IP), with its obtuse and strict UX, I was leery to try again with the IP4K. Like the PEXHDCAP, the original IP color space converts the HDMI input as well, making it impossible to get accurate pixel values from captures. Thankfully, the Pro 4K has proved to be a redemption, as you can get bit perfect captures with the IP4K! Being able to capture 1080p60 sources is a huge boon over the IP and PEXHDCAP as well.
Without further ado, here are the raw captures for the 7 palette options (4 AVS, 3 Hi-Def NES). As noted before, and now fully confirmed, the FCEUX palette on the Hi-Def NES is without a doubt, not actually the FCEUX palette, but rather a custom palette that appears to be Kevtris' own custom creation (diff comparison pictured first).