Absolutely you can return the three blocks. I'm just saying that when I do a swap like this, I always make extras for my friends who are not in the swap, but whom I would like to be on my quilt, i.e., my BF, my Mom, my Aunt, my Mom's BF, etc. I will substitute my three for some of those. I'm not saying anyone else has to. Just a suggestion if you don't want the duplicates.
Easter Blessings, Cherie