I bought my mini in late June 2013. My internal hard drive had the same cable as the one in the iFixit kit. I had to position the cable for the upper drive on top and not in-between the drives as indicated. I also had to bend the ribbon in the opposite directions. Be careful. The ribbon can be adjusted but due to the location of the sata connectors on the mainboard the cable for the upper hard drive does not lay flat against the drive. There is room for it under the vent that the wireless cable is attached to if you have the upper drive seated correctly in the grommets but it is not pretty.
I bought my mini in late June 2013. My hard drive was not mounted as indicated, it was in the lower slot. I had to insert the grommets into the upper holes. You need to use a non metal flat edge to get them in, my fingers had no leverage when reaching into the aluminum shell. I also waited until I had removed everything from the case before inserting them to minimize the risk of harming an internal component.