In plain words
Services sold under this name vary widely. LeakTrace does not crawl criminal forums: it reads monitored breach databases and paste sites and checks for keys left in your own website's code, re-checked daily for monitored firms, and a person approves every assessment before it is released.
Why it matters to a firm
What matters to a firm is not the label but what is read and how quickly a new exposure reaches the person who can act on it.
How anyone can check it
Ask any provider which sources it reads, how often, and whether a person reviews a finding before it is sent.