Sorry!, ─ that my statement is giving a cause for misinterpretation!
(When I answered you I hade (only) the carbonate statement from Mr. AWK in mind, sorry!)
Of course you are right! In case a manufacturer adds “any” Carbonate to the Tablet you will titrate the contained base too, because at the end point of your Titration, around or below pH 5.5, most or all Carbonate will be “formed” to CO2.
Such an addition will require more H2SO4 and simulate a lower Content.
But that’s also only one indication of an unspecific method.
(To stop Titration on higher pH may also have disadvantages, as collected CO2.)
Yes! ─ There are “several” reasons, like Stability (phys. & chem.) of the Formulation for different “Climates” on Earth, Hardness of Tablet, DR (Disolution Ratio), etc.
(Galenics is quite a broad field for R & D.)
Sorry to have given you a wrong cause.