That's completely not true, at least not everywhere. Last time I ordered lithium ion batteries from Amazon, the package was plastered with warnings about the dangers of lithium ion batteries.
That being said, the last time I ordered potentially dangerous chemicals from Amazon, it came in a non-descript box, and the last time I ordered furniture (from a 3rd party vendor on Amazon), it shipped in a box that had a picture and description of exactly what it was, so the only thing you can say for sure is there's no universally applicable rule.