Probably true, but my PH never seems to vary much between water changes, and if it does I have PH buffer just in case.
If you have an R/O water filter then I wouldn't worry about evaporation either, but buying jug after jug of distilled water gets expensive and a hassel. I don't have corals or anything that need high-powered lighting, so heat is not a problem . I have fish only, so small fluctuations in PH is not huge problem either.
"Ocean: A body of water occupying about two-thirds of a world made for man - who has no gills."