Not entirely true although close. If distilled water purity was equal to that of RO/DI, then labs and critical processes required pure water would be using distilled water. JMHO. Most processes I've seen with water that require purity use RO/DI. You can still have TDS in distilled water and you can still have po4 and no3 in distilled water. As you suggest, not that big of a deal as I think the problems the OP has are bigger than distilled vs. RO/DI.