And the following article refers to it as an Active/Active/Passive cluster:

Reviewing and Testing SQL Server Cluster Configuration for Failover Scenarios

You are trying to split hairs over symantics here that can confuse people that don't know enough about clustering. Multinode clusters, or N+1 clusters are commonly referred to by the setup as Active/Active/Passive, Active/Active/Active/Passive, etc by most people in the community. Your article is from 2003, mine is from a more recent version of the Books Online. It is possible that the terminology has changed slightly in the last 8 years to make it easier for people to understand the setup better.