Clarification on UK residence permit for non EEA spouse

Hello
My wife is Russian. We were married in 2003 with 2 children. We lived in Spain for 14 years and my wife has permanent Spanish residency. As I now work in the UK my wife and children have joined me here. My wife entered the UK without a family permit as we come under the "exercising treaty rights" rules.
Specifically does my wife require a residence permit and can she obtain an NI number to work without it. From my understanding and reading official sites, this is the case. On the GOV.UK page under - Apply for residence card -- it states --- You don't need to apply for a residence card as a family member -- but it can help...for various reasons...

Is this true, in my wifes circumstances?