I think they're explicitly not interested in making it healthy as compared to a beef burger. They're looking to appeal to exactly the same people that would wan

I think they're explicitly not interested in making it healthy as compared to a beef burger. They're looking to appeal to exactly the same people that would want a regular burger, and deliver as near an identical experience as possible, but with a lower carbon footprint. Products already exist on the market for health-conscious consumers, but BK customers apparently prefer burgers, health considerations notwithstanding. Presumably at least part of that preference is because they're greasy and salty and indulgent, and substitute products would need to check those same boxes to be appealing.