DOES THE HDK SUSPENSION K-MEMBER HANDLE BETTER THAN A T-BAR SUSPENSION?

I have no idea what you are talking about in your guess or reasoning.

The similarity is easy to spot, rod ends are often used to have large and finite adjustments for placement of the ball end to a fixed position that might not always be in the exact same position, car to car....K to K. Welding causes distortion, sometimes it may only be a few thousands, but having that finite adjustment is the difference whether something slides in / on smoothly or has to be beat in / on.

No engineering studies or degrees required for the above evaluation....only need to work with it. Try it sometime.
I, many replies ago, addressed what seemed to be the reason for rod ends as a lower LCA cross brace connection.. Mainly there is no "real estate" available in the existing area to weld (which would be a horrible very unfriendly user solution) or bolt a multi axis robust restraint bracket to terminate this crossmember. Adjustability is solvable other ways. A swivel joint is indeed easy way to connect but only allows restraint in one direction, but still an improvement over no connection/brace.
Monte Carlo braces are greatly handicapped with swivel connections in effectiveness, especially when braces are not straight.
This help?