Why is SharePoint saying that my Nintex 2013 workflow is being run as a 2010 workflow?
When I click on workflow settings from the List tab on my list, the workflow settings screen is showing that my workflows are 2010 but I am using Nintex Workflow for SharePoint 2013, 2016, 2019. e.g This is a article attached image
With the introduction of SharePoint 2013 Microsoft also added a new workflow engine which is known as Workflow Manager or the 2013 workflow engine. The previous engine is known as the 2010 workflow engine.
With the introduction of SharePoint 2016 and 2019 Microsoft kept these two engines so on those platforms you will still see references to 2010 and 2013.
Nintex uses the 2010 workflow engine for all our on premise versions of Nintex Workflow.
This is why your Nintex Workflows will show as 2010 workflows but this is in no way inhibits the functionality or efficiency of your workflows.
You will only see this if both engines are enabled in the environment.