"xml (boolen): if this option is activated, the values of the field don't have a linked SQL field. Adobe Campaign creates a Text type "mData" field for record storage. This means there is no filtering or sorting on these fields."
If you look in the Workflow schema and search "keepResult", it's set as xml="true". As it's highly recommended that you don't adjust anything in the out of the box schemas, the only other option could possibly be to create an extension which removes that piece, but without testing I'm not sure how exactly that works.