The opposite situation seems kind of odd though, where someone would have no booklet credits, but has ASCAP credits. For example, I'm clueless as to why Robin would have ASCAP credit on almost every Chinese Democracy song but was noted in the booklet credits for only some of those songs. I'm sure he'd rather have the $ than the recognition, but still... why not the recognition?
Steven Adler didn't write any songs on Appetite, but he still was compensated by getting part of the publishing.
Robin probably wrote guitar parts that aren't necessarily the main melody of the song. Or something.
/jarmo