Family Finder rounds off segments to the nearest block, so these regions have the appearance of identicality, but may not be exactly identical.
In any case, 3.18 cM is a very low amount, and unless you know that you are recently related to someone or your block of this size is adjacent another larger one, I would pay very little attention to any segment under about 6-8 centimorgans.
Finally, it's definitely not a waste of time to analyze the data this way for larger blocks. I have overlapping segments with a known maternal second cousin, and with a suspected paternal 4th cousin once or twice removed (we share an unusual surname). By looking at the overlap by region, I can establish which side of the chromosome pertains to which side of my family. This may also be useful if you have uploaded to gedmatch.com.