Either they used something to ID and redact every face, whoever they made redact them was tired and just went "face -> black box" without thinking, or whoever redacted it thought it would be funny and no one would care (which makes me think of the similar gag from Catch 22 about a bored soldier just redacting random words in letters home because it entertained him and no one who could punish him gave a shit as long as the important things got redacted too).