Concur. The question is whether or not the individual has, in fact, been Baptised ... and what to do if due to poor recordkeeping or dubious theology there's no certainty in the case.
That's easy: Baptize in the Name of the Father, the Son and the Holy Ghost, by triple immersion. :)
The real problem is when there is a good possibility that a person would be re-baptized or "double bpatized" through negligence.
The bishop is then probably under his own obligation to investigate the parish practices and determine how it is done, and make a decision based on that.
But I am sure, the bishop will wish to remove all doubt before subjecting someone to another Baptism.