Environment ActiveGates are downloaded from one environment and normally will be used by only one environment but if you make the configuration changes noted there then they can be shared by a number of environments in your managed cluster.
On the other hand Cluster ActiveGates will be able to be used by EVERY environment in your cluster. So it depends on your needs and architecture; sometimes you may not want to have an environment activegate for every environment but at the same time you may not want all of your environments able to use an activegate due to locations etc... so in that case you can just use an environment activegate and configure it to be shared by a subset of your environments.
No contradiction, just different use cases.
James
