AD&D Toys and Quest for the Heartstone

Maybe somebody out there can explain this to me. The toy line from the 80s was branded as Advanced Dungeons and Dragons, yeah? (Official Advanced Dungeons & Dragons, no less!)

So why did the characters from the AD&D toy line only appear in a Basic Dungeons & Dragons module, XL-1: Quest for the Heartstone?

This is a completely unimportant question, but I've always wondered what happened there. 

I still have a few AD&D toys from my childhood; I've got an ogre, a roper, a carrion crawler, a Strongheart, and the bronze dragon. Oddly enough, I was able to buy a Warduke and a nightmare as a highschooler (about a decade after they first hit shelves) from a failing chain store that only seemed to stock toys that were discovered in the backs of warehouses ten years down the road. Thanks, Ames! (Sorry all your stores closed.)