The New York state assemblyman who proposed banning all salt from restaurants, Felix Ortiz, has been around long enough to know it has absolutely zero chance of passing. So he probably proposed it knowing it was absurd but that he would get a lot of media attention and a chance to discuss the health dangers of salt on a national platform. His district has a lot of health problems, and salt over-consumption is part of that. (I doubt he's using it to get national media attention just for the attention, as I don't believe he's ever run for higher office.)
Ortiz did something similar when he proposed legislation to lower the drinking age to 18. Any state legislature is extremely unlikely to unilaterally lower the drinking age because their state would simply lose too much federal funding. Ortiz just wanted a chance to talk on a national platform about how over-enforcement of 18 to 20-year olds can be damaging, and he got it.
Bottom line, I doubt he really wants to ban salt. But he does want to get people thinking about salt as a health danger, which he's accomplished, and maybe to inspire a reduction in salt consumption. After all, proposals to limit the usage of salt in restaurants have been floating around for a while, particularly in New York. Proposing an all-out ban is a good idea in that it makes more modest regulations look more reasonable. But that said, this is Albany, so really anything is possible.