It applies to molecules (e.g. BPA), where a single atom substitution gives you a new molecule. So it's like saying you can't make a navy shirt with exactly 44 stripes on it - you just make one with 45. Or change the hue slightly. It makes no real difference.

Sulfur is an element, so it's a whole different category of discussion. It's like saying "you have to use less cotton." You might replace it with silk or rayon or just make fewer shirts, but it's a much more impactful restriction.

CFCs aren't a specific molecule, but a class of molecules: they're organic compounds of usually 1-4 carbons that have (some number) of chlorine and some number of fluorine atoms on them. Here you can't just swap one fluorine for one hydrogen and squeak past the regs, because you're still in the same class. It's like a regulation barring button-down shirts: one button more or less isn't going to let you avoid the rules, though you can still make shirts of some variety.

This is why regs targeting classes are far more effective than those targeting single molecules.

Sulfur in fuel is a contaminant. It isn't added, it was there when the crude was pumped out of the ground. Once you remove it you don't need to replace it with anything. The oil industry has claimed the sulfur was useful as a lubricant, but that was largely a red herring because they didn't want to pay to remove it.

And CFCs were used for their physical properties rather than their chemical properties, so it's possible to substitute compounds that are chemically different as long as they still have the right physical properties.

A good example on the other side is fire retardant chemicals used in furniture. They're pretty much all toxic, so every few years the most recently popular one gets banned and the manufacturers switch to something else which is just as bad but isn't prohibited yet.