Haha, agreed that it is somewhat tacky, but the original question wasn't concerned with tackiness.
If this issue is a concern, perhaps a more suitable way of stating one was qualified for the honor should be used. That is the point, after all, no? Is the fact that one didn't spend the three years as an NSF pre-doc as important as the fact that one was qualified for it? Does accepting the fellowship and using its three years of funding somehow make one more qualified? As long as one continues to meet the stipulations for funding throughout their graduate work, being qualified for the honor and actually utilizing it are not so completely different (notwithstanding is the prior discussion of preferential treatment by NSF in the future according to whether one has been funded by them). Moreover, some other more prestigious fellowship likely took its place if one is in a position to decline, so it's simply one more way to draw attention to one's qualifications, which seems to be the point of CVs.