Don't want to mention the company, but they have a product that is pure powdered vanilla (contains maltodextrin, whatever that is). They say it prevents melted chocolate from seizing. Does that sound right?
I just reviewed the Nielsen Massey website and under their FAQ's they suggest that vanilla powder be used for "liquid sensitive products". The powdered nature of the vanilla would allow you to add it to melted chocolate without causing the melted chocolate to seize up. While vanilla has a unique and characteristic flavor of its own, it also helps to heighten and intensify other flavors, chocolate being one of them.
When chocolate seizes the emulsion of cocoa butter and cocoa powder has been interrupted by the introduction of a small amount of moisture. You either need to keep all liquids out of melted chocolate or add in a significant amount.
So...it only prevents it from seizing if you were going to be adding vanilla in extract form but no other liquids. It would not be something you add as a preventative measure.
Prevent the seizing through proper procedures in the first place:
I'm not familiar with the anti-seize property, but I can tell you what (tapioca) maltodextrin is. It is a modified food starch with the amazing property that it thickens fat instead of water-based liquids. If you have ever eaten at a restaurant that does the molecular-gastronomy schtick and had a powdered olive oil or coconut oil, e.g., that is how it is made.