Possibly Dr Tim thought if people added stuff they may not remove it by a big water change at the end. Yes, doing a water change every time pH drops is one way of dealing with it, but that would mean a lot of large water changes with a 65 gallon tank. Adding baking soda not only increases pH it adds inorganic carbon which is what the bacteria need.
Check the Jack Dempsey's GH range on Seriously Fish (it's down at the moment so I can't check). They'll give it either ppm or dH (see post #38 for yuor values)
www.seriouslyfish.com
I agree, it's not a good idea taking media from a newly cycled tank. it takes around 6 months for a tank to mature, that's when it's safe to donate media.