I understand less about the specifics of their mtDNA forensic system than the nuclear system (where it's clear which "bits" of the genome are examined and how many).
IMO, confusion was created by saying that the result corresponded to x "or an individual of the same maternal bloodline". While it is true that mtDNA is inherited via the mother to all the children, the EMPOP database first went online in 2006 and - IMO - was comparatively in its infancy for forensic purposes.
For example, Kate shares the same haplotype as one of the first GNR officers on the scene (Jose Roque)... yet I have seen nothing to date to suggest that they are siblings.
https://www.mccannpjfiles.co.uk/P16/16_VOLUME_XVIa_Page_4175.jpgIn their database, there were 8 separate maternal lines with the same haplotype as JT's out of their nascent database of 3000 ish.
The EMPOP mtDNA database
On October 16, 2006, release I of the EMPOP database went online [Parson 2007b]. It is an IT based, open platform for comparison and storage of mtDNA sequence data and comprises 5173 mtDNA sequences from worldwide populations contributed by laboratories that had successfully participated in collaborative exercises. 4527 sequences are forensic data (high quality sequences), 646 sequences in the database are validated sequence data from publications, where raw data are not available. Literature-derived sequences have been carefully inspected with several methods of phylogenetic evaluation. The majority of the 5173 sequences derive from Western Eurasian populations, smaller datasets from East Asian, South East Asian and Subsahara African (meta)populations. Ongoing sampling and analysis is continuously increasing the number of samples and worldwide regions covered. Three PhD students at the Innsbruck Institute of Legal Medicine work in this field investigating populations currently underrepresented not only in in the EMPOP database.
https://genomics.gmi.tirol/projects/empop/On the West Eurasia categories:
More than three-quarters of the present-day European mtDNA gene pool most likely comes from indigenous Mesolithic or Palaeolithic ancestors. In addition Neolithic immigrants, who brought the first forms of agriculture to the hunter-gatherer dominated European landscape, ~8,000 years ago play an important part of today’s mtDNA pool of modern humans in West Eurasia [Richards 2000].https://genomics.gmi.tirol/projects/empop/west-eurasia/