Didn't earth glide and similar not function with worked stone? Or does that class override that?
Earth elemental's entry says nothing about that... you have a source?
In Pathfinder, one of the earth glide spells has a 'no worked stone' clause. That's probably what he's thinking of.
EDIT: Incidentally, I'm currently putting together an Illusionist Wizard/Shadowcraft Mage/Earth Dreamer character for an upcoming game. Little different than this, but some cool options. Race wise, I'm being a Lesser Mechanatrix, and taking extra familiar and improved familiar for Shocker Lizard buddies who can heal me in combat at level 5. Playing up an electrical/crystal theme, which helps because Mechanatrixes sort of look like Genasi from the description- so I'm going all glowy lines
technology magic, and theming the Shadowcraft mage's adaption for being a cabal that holds the secrets of altering the laws of reality via shadowcraft and the earth dream, connecting to a shard of Mechanus.
It'd be great to go cleric or archivist, but even with flaws I'm pretty low on feats, and I want the double improved familiar up as early as possible.