That’s a standard product used widely in the industry. It will help to reduce calcium dust during plaster hydration and carbonation. It is a diphosphonic acid eventually breaks down into orthophosphates. It’s fine to use during startup.
[EDIT]
Based on the orenda website, they say it’s not a phosphate based anionic compound. They might be using a poly anionic chelating agent. There are many based on carboxylic acid but they are typically more expensive and less effective than phosphate based chelating agents. There are also ammonium based chelating agents as well, but those would cause chlorine demand and form CCs from oxidation.
Either way, the use of a sequestering agent at startup is standard practice and will have no long term consequences. Just don’t get roped into using them on a regular basis as it is unnecessary unless you have an established metal problem with your fill water.
[END-EDIT]