It appears that this article has been changed (or at least republished). Perry Whittle's comment should have been taken into consideration, the difference between RAID 1+0 and 0+1 is indeed not academic. RAID 1+0 is a stripe of mirrors, if one disk fails, that mirror has only one disk left, but all the other mirrors may still lose a disk each, and your RAID array is still available. RAID 0+1 is a mirror of stripes, if one disk fails, that whole stripe is available, and you're left with a singe stripe. If one of the disks in this stripe fails, your RAID array is not available anymore.

As far as I understand it, the physical storage of RAID 1+0 and 0+1 are identical, the difference lays in how these data are used logically (or internally if you wish) by the RAID controller.