Well, you are both right!
Grodan originally said to soak for 24 hours, but has recently changed their directions to 30 minutes. So it's not the amount of time that is important, it's the pH. Rockwool is spun rock, and some of the rock is limestone. There may be residual lime in the rockwool, and lime, as we all know from our reading, raises pH. So the wetting of the rockwool is done with a low pH soup, to fix the lime.
Lower your soak solution to the low 5's, using pH Down, or a Bloom nutrient.
After your soak, rewet with a low-strength nute soup, pH 5.8, and plant away.
HTH