info.magnolia.ui.workbench.column.definition.AbstractColumnDefinition defines sortable as false by default. However, extensions of this such as PropertyColumnDefinition and StatusColumnDefinition are rendered with headers which, when clicked, display up/down arrows. Further, the clicking can have an effect on the data.

Having defined the column as sortable=false (either explicitly or by not overriding the default) I would expect it to ignore clicks, as per the documentation.