Question

an we take an "action plan" as the example of "technical writing"?

Answer 1

I suppose if the activity plan or action plan is distributed or messaged to others, and if the activities in that are depicted at an adequately specialized level of detail, at that point an action plan may be viewed as technical writing. Review that "specialized" means doing with the procedure, that is involving "how" something is done, methods connected. 
One may make an action plan for instance of specialized written work. Specialized composition, notwithstanding, is substantially more extensive than a single illustration.

Answer 2

Action plan

It is a detailed plan which outlines the actions required to reach one or more goals. It is a sequence of steps which must be taken, or activities which must be performed properly for the success of a strategy.

Technical writing

It is a type of writing where the author writes about a particular subject which needs direction, instruction, or explanation. It is sometimes defined as simplifying the complex. It involves communicating complex information to those who require it to accomplish some goal or task.

 

An action plan can be informal or formal. It need not follow the rules of technical writing. But an action plan can be a part of technical documentation, for example, an action plan for customers or developers.

In some cases an 'action plan' can be considered as an example of 'technical writing'. Particularly if it mentions specific facts, timelines, figures, personnel deployment, skill levels and other details.