he was talking about scope here. hashes do not help much.
assoc lists were important to implement dynamic environments simple and fast, which is not so easy with hash tables. In assoc lists you tolerate duplicates, but by putting new at the beginning you override/"shadow" the old ones, until you leave scope and use the old assoc list. and share the data! with hashes you have to actively delete or copy the tables. non-efficient and very complicated.
assoc lists were important to implement dynamic environments simple and fast, which is not so easy with hash tables. In assoc lists you tolerate duplicates, but by putting new at the beginning you override/"shadow" the old ones, until you leave scope and use the old assoc list. and share the data! with hashes you have to actively delete or copy the tables. non-efficient and very complicated.