Wouldn't it depend on the comparison?
Since their baseline is the 7600k @ 100%, Zen is 150% and Zen+ is 170%, then one can say, in this test, Zen+ is 20% faster than Zen. (Since we are comparing against the 100% baseline) which is why I don't like those comparisons at all
If one is 150% and the other is 170% then the second chip is 13% faster, not 20%.