You're right:
- product is called GitHub Actions
- your workflow (consisting of jobs and steps) is a workflow
- 3rd party workflow included in yours is an action, not workflow though
- I more often hear engineers refer to workflows as actions
But there are more annoying decisions
- (org-wide) required workflows being recently deprecated
- the feature was buggy (ie used alongside org-wide branch rules)
- but could have been fixed, not deprecated
- some kind of "marketplace" (with reviews, developers trust levels etc) for modular/pluggable actions (workflows) would be welcome; currently it's a "1st solution fitting the problem used" mess with little to no standarisation
- I find the necessity to write a step cloning the repo from which a workflow is running ridiculous - it should be at most a single configuration line somewhere at the top of a workflow
Not entirely accurate. You can use reusable workflows from third parties and you can use actions from third parties. It being a third party's doesn't mean it's an action. Also, you can make your own actions, it doesn't need to be a third party's.
Just to add to the naming confusion.