>>12998958I was gonna say that I trust the "British Journal of Anaesthesia" more than you, but then I found another source which reads like yours.
So I looked into it more deeply and found the resolution:
>Most of the carbon dioxide diffusing through the capillaries and ultimately into the red blood cells combines with water via a chemical reaction catalyzed by the enzyme carbonic anhydrase catalyzes, forming carbonic acid. So apparently it's not just the stuff that's bound to the hemoglobin that's being transported in the RBC, carbonic acid is just hanging out in the cells.
Source: (Physiology, Carbon Dioxide Transport, 2020).
