GM said in the past to mix Dex-Cool concentrate with drinkable(potable) water but said for the inverter/electronics coolant for a Volt/Bolt to use only premixed Dex. Scale can hinder cooling in an ICE, but in the inverter of a hybrid or BEV a blocked cooling channel can fry a IBGT or MOSFET used to switch or amplify power to the drive motor/generators.
Prestone has put on the back label of their concentrated coolants: Water quality matters - mix only with distilled water.
Some coolant inhibitors, especially phosphate are effective sequestering agents - with an affinity for sodium/calcium/potassium ions. There’s good reason why the Europeans didn’t favor phosphates in their coolant with their harder water. On a side note, German washer fluid concentrate such as Einszett Krystal Klar or Mercedes Summer-Fit(the mix ratio is 1:100 to 1:192) uses sodium docusate(yes, stool softener) for the same sequestering effect.