It is another tool to justify police action with a low true positive rate.
"We were following the AI leads" is the perfect excuse for parallel construction[1] (evidence laundering).
If Rekognition supports limiting the search to the people in a specific town (or other small group), it might be possible to force someone to be somewhere on the list of matches. That would give bad actors the perfect tool for manufacturing "probable cause".
You're assuming that there is a wide distribution of confidence levels in every search. Its very possible with grainy footage that no result is above a reasonable threshold, but the results will still show an ordered list.
Without _some_ threshold or training in what these kind of scores mean, its easy for a user to think "well they were the best match" and take a negative action like bringing them in for questioning or introducing the match as evidence, even if its only 10% +/- 5%.
(I could be missing something here)
Thresholding is not the only way to make use of a classifier that ouputs a confidence score. In particular, the slide shown in the article indicates that they use the confidence score to sort search results in descending order. That means that there is no fixed threshold and the PIO's statement is not worrisome at all.
The system described is much less dangerous (in terms of overconfident decisions) than one that only returns results matching a threshold, because it means that the user also occasionally sees low-confidence results and learns that they can't simply defer decisions to the machine.