100% correct!

And since carbonic acid/bicarb is the main buffer in blood, we regulate that by regulating our breathing. CO2 is converted into carbonic acid so by holding our breath (or breathing slower), we retain CO2 and decrease blood pH. Inversely, by breathing faster we blow out more CO2 and increase our blood pH.

Decreased blood pH is one of the main drivers for breathing. When you're swimming underwater and you start to feel the urge to breathe, it isn't lack of oxygen but rather the decreased blood pH from retained CO2 that your brain is sensing.

As a short aside, it's really bad for your blood to be more acidic OR more basic than ~7.4 pH. So when you see products claiming to "alkalinize" your body/blood for health, it's complete BS. Acids and bases are not inherently bad or good just like how hot and cold things are not inherently bad or good. I see these ads pop up pretty frequently, especially in fitness related settings and it drives me nuts.