In the same review that states "warnings on the box are a bit worrisome" as a con, they tell you that the box states "This product is sold and should be used as an adult novelty only, and should never be other than for external use".
This is a VERY common warning on sex toys. There are a few reasons for this. One reason could be that they want to avoid certain lawsuits by having the warning, just in case. But the biggest reason is that the product could be made in China (or possibly a similar country), where selling sex toys is illegal. That's why they brand them "novelty" items so they can bypass the laws.