The confusion comes in the unit of calcium (ppm) and Alk (dkh etc).
If one measure calcium and carbonate (major part of alkalinity) in ppm, they do not get consumed at the same ppm due to they have different molecular weight.
But when coral forms its skeleton in calcium carbonate, it is one calcium binds to one carbonate.
If one wants to go into academic exercise, Indeed it is not 100% at 1:1 ratio. Because what all the hobby grade test kits measuring is the total alkalinity, not the concentration of carbonate. Even more confusing is that alkalinity is not a single element like calcium, it is the buffering capacity of the water, which affected by many different elements.
If we want to go deeper, many cans of worms will be opened and it will make people so confused.
But the difference is so small that it is beyond hobby grade test kits can measure. Also the small difference is not important nor applicable to this hobby.
The bottom line is by dosing commercial calcium and alkalinity solutions at 1:1 volume ratio, you will be fine. Monitor Alkalinity often and spot check your calcium level once a while. Or even better, use a calcium reactor with Reborn reactor media, only check the Alk level and forget about all these dosing mess.