"...I am still trying to understand if programmability of the TPM within the LaGrande/NGSCB architecture is an enhancement providing additional functionality, or if it would be redundant to LaGrande/NGSCB?..."
Redundant! The only benefit would be that encryption algorithms could be updated/reprogrammed.
NGSCB's secure execution environment idea is virtually identical to the E2100 Trust System. I wonder why!