Huh? If it were simply nulling it you would have silent spots instead of click. Any software which is removing a click is creating something to put in it's place.I don't know about CR.
I can say that iZotopeRZ works by isolating the click artifact and then nulling it out. If you use the 'output clicks' function and zoom in on the results, you'll see. So it's not removing an entire slice of time which would then have to be replaced with something. It's isolating JUST the click artifact (spectral-ly), polarity reversing it, and mixing it back in to remove it from the source.
Older click repair tools may be doing something like slice and replace. I'm pretty sure that's what the old real time units did. It turns out that a lot of vinyl click and pop artifacts are so much more dynamic/transient than the music that even the older cruder methods can yield good results. You can really get artifact/loss free results with iZotope though.
CR also has the output clicks monitoring function.