I don’t know, seems reasonable to me. How many people on the street would know when asked what the safe dosage of liquorice is? Guess most would say it’s no worse than any sugary candy. Is it not similar to an allergy?
The inverse to "not safe" isn't "good for their health", but "safe" (or at least not less safe than one would expect - i.e. that much sweet liquorice is also going to have a bunch of sugar, which is both widely known and documented on the packaging), which is more reasonable to think.