This is a very inaccurate article that makes a ton of assumptions about Nassarius snails and whelks based on a limited number of species. In particular, multiple species of Nassarius snails do indeed feature patterned siphons (ex. Nassarius margaritifer) and some whelks, like Kellet's whelk (Kelletia kelletii) lack patterning on their siphons.That isn't a nass snail. Its a whelk. Look a the siphon, if it looks tattooed, its a whelk. good article.
Whelk versus Nassarius | Melev's Reef
www.melevsreef.com