This is true, and it is presumably related to an obligation established under the federal/state child support program for a dependent child. If there is no findings on the record of dependency, there can be no "absent parent" under that program, and the court would have no jurisdiction of such a cause. The reason you can find no published appellate opinions is because jurisdiction was properly desided at the district court level, or nobody has brought such a motion and appealed an adverse desision. I wouldn't say it's a matter of practice, without seeing such a case that was pressed on that particular issue, as we are now attempting to do here in Minnesota. I have seen a case remanded back to the district court for findings of dependency. I'll find you the case if you're interested.
Please do. I spent a couple of hours today on lexisone.com looking up recent cases...That site comes in handy.