Nay, 'tis not so! But even so, adding salt to pasta cooking water is a good idea.
What Does Adding Salt to Pasta Water Actually Do?
Well, it certainly does not reduce time to boil and in fact increases it a tiny bit. Adding a typical amount of salt will increase the boiling point by a few hundredths of a degree, which is meaningless in practice. Boiling wise, adding salt is irrelevant.
But adding salt to the water is important from a flavor perspective. It allows a bit of salt to soak into the pasta during cooking. This gives better flavor than unsalted water, where the only salt comes later from the sauce which is on the surface of the pasta.
Salting Pasta Water in Italy
Salting the pasta water is a given in Italy. Unsalted pasta water produces pasta Italians call “sciocca,” which means “silly” or “foolish”—a pretty clear statement of how they feel about it. Italian cooking sources often suggest roughly 10 g of salt per liter of water, often expressed as the “1–10–100” rule: 1 liter water, 10 g salt, 100 g pasta. Translated, this is roughly 1 quart of water, 1/2 tablespoon of table salt, and 3-1/2 ounces of pasta. This will be adjusted as needed depending on the saltiness of the sauce to be used.
Small correction, your conclusion holds. The post says a typical amount of salt lifts the boiling point “by a few hundredths of a degree.” With the 1-10-100 rule you cite two paragraphs later (10 g salt per liter), it’s about 0.16 C, so roughly an order of magnitude more than hundredths.
Sourced half: water’s molal boiling-point elevation constant is 0.512 C kg/mol. 10 g of NaCl in a liter (about 1 kg) of water is 0.171 mol, which gives 0.171 mol/kg. NaCl splits into two ions, and the measured van’t Hoff factor is about 1.8, not the ideal 2. 0.512 x 0.171 x 1.8 = 0.16 C. Lumen’s general chemistry text puts the scale plainly: you would need over 100 g of NaCl per liter to move the boiling point a couple of degrees.
My own read, not sourced: that still lands exactly where you land it, meaningless in practice, and it does not rescue the “boils sooner” myth. A tenth of a degree just costs you a hair more time, not less. But if a reader checks the arithmetic against the salt amount you recommend, “hundredths” is the one number in an otherwise solid post that won’t hold.