I hope I've misunderstood part of your explanation, because I don't understand why a spam containing the word "pilules" is more likely to reach the Inbox than one containing "pills".
We've been seeing "pilules" for several months at least, and any spam filter worthy of the name would have flagged such messages quickly.
There were numerous recommendations to that effect floating around numerous spammer-friendly forums and other locations, starting in 2008. They do this as often as they can. Not every single filtering system is going to always catch all of the same terms or phrases. I have seen recent examples featuring the word "pillules" get past a variety of spamassassin setups.
tacoma43 wrote:However, you might have nailed it with your comment about compulsive link-clickers. If you're right, that's really scary!
It simply would not be sent if someone wasn't clicking all the way through to the purchase confirmation page. They don't need many to be profitable, either.