Alkoxy cure is the cure that you smell, for instance when you apply a sealant and you get that very strong vinegar odor. That’s the release of the acidic acid and that’s how the silicone is curing. A lot of times those particular silicones are used very frequently in bathroom or kitchen environments, particularly where you want to reduce mildew because they’re very good at that.
Neutral cure silicones rely on the exposure to air. The only thing that you typically release with them is an alcohol or another compound. You don’t get the shrinkage with that and you don’t get that strong acidic or vinegar odor that you get from alkoxy.