Curiosity falls under the "stimulation" heading, as does skill acquisition for its own sake (e.g. video games).

To be fair, the SASS list is more a convenient set of categories, than it is an attempt to be a comprehensive and rigorously-proven classification system. However, it's definitely "less wrong" than assuming everything is about status... yet not so unwieldy as the systems that claim 16 or more basic human drives.