Please! This is not true!

Di-Chlor WILL lower your pH of your pool, just not as much as Tri-Chlor. I cannot reconstruct all the chemistry for you, but the gist is, that while Di-Chlor itself is neutral, the reaction from the chlorine lowers pH. I'm sure our chem whiz, Chem_Geek can show the chemical equations to demonstrate, but from my empirical experience I know it to be true.

Bleach is actually a high pH chemical, but the same reaction of the chlorine lowering pH just offsets the increasing effect of the Bleach. This is why Bleach/Liquid Chlorine is the ONLY pH neutral chlorine source.

Carl