Armory would probably have used BIP-32 as well, but was developed before BIP-32 was created.
Armory's wallet design was based on BIP32 in an early stage of it's evolution, I believe. But BIP32 changed after the fact, and then took a while to get adopted by wallet software.
AFAIK, Armory introduced hierarchical deterministic wallets to the ecosystem. This in turn inspired BIP32 which improved the design while standardizing the feature.