This isn't a Core-Only concept to begin with.
Jaronk's comment about using less books (guess what, it always will since items/feats are the only noncore thing an adapt can have) is being taken way out of parturition.
The debate here isn't about core versus non-core. The debate is about the degree to which each build relies on material beyond its initial printing.
Giacomo's monk uses five books for six substitution levels (Player's Handbook 2, Exemplars of Evil, Complete Champion, Dungeonscape, Planar Handbook); Tome of Battle for Martial Stance, Snap Kick, the discipline weapon property, and a maneuver-granting item; Complete Champion again for Knowledge Devotion; Complete Scoundrel for skill tricks; Unearthed Arcana for Item Familiar; Complete Warrior for Rapid Stunning; Magic Item Compendium for the Scout's Headband, Third Eye Improvisation, Ghost Shroud, Winged Vest, Greatreach Bracers, Ki Straps, Healing Belt, Torc of the Titans, and Heartseeking Amulet; Dragon Magic for the Fanged Ring; and Savage Species for the Necklace of Natural Attack. I think that's everything, which amounts to twelve sourcebooks outside of core.
JaronK's adept, on the other hand, uses Libris Mortis for Corpse Crafter, Mother Cyst, and Nimble Bones. Oh, and Tome of Battle for a maneuver-granting item. That's two additional sourcebooks. If we were to take your stance that only items and feats count in this respect because those are available to both parties, we have eight sourcebooks to two.
Granted, if we take the class and available material as a whole, the amount of sourcebooks used is meaningless. However, I'd invite everyone to consider a quote from Giacomo himself:
To illustrate how much the expert uses his class abilities you say it is way less item-dependent than the monk, but the whole point is not about magic item dependence, but how much additional stuff (mundane items, rituals, magic buffs and magic items) in total you need to perform.
In terms of "additional stuff," the monk uses quite a bit more than the adept, and there's still some debate as to whether the monk can perform as advertised.