It is true. Do a search for CO2 hydration.
While the proportion of carbonic acid is low, it is a time and temperature dependent reaction and we know that the quality of carbonation improves with time, even though we can get a bunch of carbon dioxide into solution in a very short time. I contend that it is the CO2 hydration that affects carbonation quality, not quantity.
If this is true, then I would think the "pump up the pressure and shake" method would be even less desireable, no?