They talk around it and try to couch it in scientific jargon, it sounds like they’re using it to produce lactic acid only, so no alcohol, which is then sterilised and filtered to death before being used as an additive.
Seems like a lot of work to make sour beer, but I have no doubt these will sell out in no time regardless, due to the provenance.
And this all assumes that they aren’t just lieing about it.
And I had to ask, because it sounds a lot like a recipe for snake oil.