New reduceLog setting changes default behavior, and if plugin is being used as a Build Step there is no way to restore the old behavior through the GUI.  If the plugin is used as Post-build Action, the GUI does show the new checkbox under Advanced.

Looking at the source, the setting was added to

src/main/resources/org/jenkinsci/plugins/xunit/XUnitPublisher

but not to

src/main/resources/org/jenkinsci/plugins/xunit/XUnitBuilder

The two sets of settings look to like they should be the same.  Adding the new checkbox  and properties to the XUnitBuilder resources gives the desired result, but if the settings are intended to be identical, combining these to a single point of maintenance would be preferable.  As it is, the title and description for the report time margin are also out of sync between the two.