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.
Right, in those days Alan Reiner/etotheipi was pretty active on bitcoin dev mailing lists and places like that, and I'm pretty sure he discussed the ideas with everyone. Was it actually Alan's idea to begin with? I can't remember that exactly.
Alan definitely just went ahead and implemented his design, whereas other wallets took a long time to follow.