Tools and joining a network

I am running the network assistant.

Explore to find a network finds the network ( and the only 1 in this case )

Try to join it and the network is marked ‘this network does not allow joining’

The co-ordinator of the network has the NJ parameter set to FF ( always join ) setting it to 0 allows joining.

Is this a typo/errata?

No that is not. If the coordinator is in range and NJ is set to FF, and the device that is requesting to join is a parent router, it should be allowed to join.