The first part this article is impracticle and misleading. The dominate factor of trace inductance is loop area and not length. Two 5 inch traces (drive and return) routed 1 inch apart would have much more inductance than the same traces routed 0.01 inches apart on a single layer board. The reason that adding the ground plane helps is that the effective area is reduces since the distance between the traces is reduced. For real life engineering, theoretical calculations of per unit length inductance of traces in free space with no consideration of return path are worthless.
Yes, the units for the left half of table 2 (and in the accompanying equation) should be mm, not cm, and the inductances/mm in the third column should be divided by 10. OR, the numbers in the first two columns could be divided by 10.