Firstly, let's acknowledge that yes, the documentation is sometimes out of sync and there are documents which use older terminology still. I'd like to try and respond while avoiding the use of terms SAC-T and SAC, CB and CBB and respond to what I feel is the underlying question regarding the intent of this release:
- Microsoft has released the April 2018 Feature update (aka 1803) for customers to use. The next Feature Update will be September 2018 or thereabouts (1809 or RS5) although we will still have Quality Updates released between now and then.
- Plan and Prepare or Evaluate phase: If you were registered in the https://insider.windows.com/, you will have had a while to do compatibility testing and to learn the new features and planned how to deploy these to meet your needs, in which case you can skip to the validation phase below. But if you haven't been leveraging the Windows insider Program, this may be the first time you've had to deploy these features. In which case we suggest you begin with an initial test and planning phase now, although Microsoft does not believe there will be many compatibility issues per se. This phase will take as long as you feel is required, typically weeks. Of course, the longer it takes to deploy the latest productivity, deployment, security features, and also the less time you have for use in the servicing window (which is 18 months after the update was released).
- Target Pilot or Validation Phase: Once planning and preparation is complete, Microsoft suggests you deploy the Feature Update to a limited selection of devices so you can validate the new features work as planned, and ensure there are no issues when deployed to your environment. You may call this deployment ring, group, or collection what you will. Some people will refer to it as SAC-T or SAC(T) or SAC (Targeted) - either way, this is it's a targeted set of devices for the 1803 release. Some people refer to it as ring 1 or 2.
- Broad deployment(s): The next deployment phase (after validation) is to reach a wider set of devices. This may be deployed to devices across the organisation, or via a self-nomination/subscription method. There may be multiple deployments to reach all of the organisation, depending on organisation deployment tools and techniques, network constraints, organisational structure, etc.
In short, I wouldn't let the terminology get in the way of the process of starting small and deploying wider. In this regard, we haven't changed anything. Typically, Microsoft envisage three (or even four) different releases of Windows being in use in the same organisation. Today, in an organisation set up to stay current with Windows as a Service, most will be on the previous release (1709 or RS3) while the new release is being deployed (1803 or RS4) and a few select devices will be enrolled on the Windows Insider Program (Slow, Fast and/or pre-release) to start planning and preparing for the next release (1809 or RS5 updates are available in the https://insider.windows.com/now)
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