It's quite simple, though. One degree drop in pH means tenfold increase of CO2 content, but you can't take for granted that outgassed water contains 3 ppm CO2. It depends, among others, on alkalinity.We're not doing a PhD thesis here.
My apology, I've obviously misunderstood your point. Yes, I agree, a water with very low alkalinity is prone to unexpected changes in pH. Plenty of personal experience.If you would have quoted my full sentence, the argument would be entirely different.