I suppose releasing the photo is still better than nothing because BG is also identified as appears to be a white male. That reduces the possibility, not a female, not of a different ethnic group and by visual deduction not a very tiny or large person. But considering the quality of the photo that LE was able to create from the video, it would be extremely unlikely that they ever expected to identify any one suspect based on only a comparison.
"Investigators have distributed a photo (shown above) of a person observed on the Delphi Historic Trail. The photo appears to depict a White male wearing blue jeans, a blue coat/jacket, and a hoodie. During the course of the investigation, preliminary evidence has led investigators to believe the aforementioned person is suspected of being involved in the murders of Abigail Williams and Liberty German."
https://www.fbi.gov/wanted/seeking-info/abigail-williams/@@download.pdf
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