One should change dd(8) into dd(1) in the following sentence : A possible method is using dd(8) to copy the data onto a good disk.
# man 8 xfs_repair The sentence is last one in "Disk Errors" section.
I realized that I should submit this bug to oss.sgi.com/projects/xfs. Hence I did it. The bug id is 1060 in their bugzilla system.