Generally 'alternative' sites like that put warning stamps on it, just in case they get the FDA on their ass, selfprotection.
thats not to say there are no dangerous herbs, but overall its definately over-exaggerated. and if you start googling for it you'll always find something. nothing wrong with herbs, nothing. based on nothing. the 3 months and then back-off is not necessary either imho. most herbal products (healthfoodstore) on the market are ineffective to begin with. processed food is more dangerous then herbs
in general no we dont have to be carefull with herbs because its a whole-food item.
medication is a synthetic isolated version of plant/herb/urine/whatever of the so called 'effective' ingredient. they have to do that else they cant put their stamp on it. cant patent nature so herbs are a bad idea for pharmaceutical industry, because what would happen if people actually figured out herbs are usefull! gone industry.