The reason why I prefer the caps to remain with the bodies is that the caps and bodies are machined as one. Then the cap is parted from the body, faced and de-burred. Meanwhile, the bodies are slotted and de-burred. Then the caps are re-mated to the bodies with the 18-8 socket caps and the whole assembly is finished as a unit again. Because of the tolerances involved between the cap and body, it is better to keep the respective caps with the respective bodies. I'm not saying they won't interchange because they will. The reason I prefer them to remain with their original body is that I mate each one and check the concentricity. To interchange them might allow the cap to become slightly offset on the body itself simply because of the tolerances involved in the indexing operation. In regard to the indexing operation, the holes are exactly 180 degrees +- 3 seconds apart. That also causes the cap to align properly. If you don't seat the cap , that is cock the cap slightly when you screw it down, it will bind. That's due to the tight tolerance between the cap and the and the threaded caps screws that secure it. Also, there is also only 0.001" of clearance between the major diameter of the socket set screw thread and the clearance hole in the bottom of the cap below the countersink. That clearance is tight purposely. That tight clearance causes the cap to symmetrically aligned with the body when it's tightened down with the 18-8 socket caps.
That's why I prefer the caps to stay with their respective bodies. I could have made the through clearances sloppy enough to allow any cap to fit any body where the end user (you) would align the caps manually, but that's not how I do things. I want each and every FlipMeister Billet Stainless Brake Line Clamp that leaves here fitting and looking good enough to mount on my R3 and be proud of.
That should explain why I state specifically to keep the respective caps and bodies together. It just makes assembly easier and allows you to have a perfect looking brake line clamp.