No... it reduces the focusing distance. At the expense of a lil light loss and slightly lower picture quality. But it's definitely much better than just a macro converter filter in front.
1:1 doens't dpeend on how far the lens is from the subject.
1:1 means that the image will be reproduced life size on the film negative or CCD (in the case of digital).
IN the film days, 35mm film is 24mm x 36mm. If you take a 1:1 reproduction of a 2cm diameter coin, it will appear as 2cm size on the film itself (which means that even at 3R, its one heck of a big coin).
Unless you're shooting insects or very very small things, most people don't need 1:1 even for macro work. For Full Frame, the question is, are you shooting objects smaller than 24mm x 36mm?