Some napkin math suggests that there are enough retail trades (8.1M/day) that under some weak constraints (most are for short-term positions, higher market cap stocks are more likely to be purchased) you're still quite likely to find a few people who have "established a pattern" quite by accident.

As long as they're just investigating and not necessarily prosecuting every event that probably sounds fine (I'd be curious to know what the prosecution "funnel" looks like for flagged individuals in real life -- 100%? 1%?), but it's important not to let an intuitive sense for things that are definitely too unlikely to happen by chance to cloud our judgement and create something like another Sally Clark event[0].

[0] https://en.wikipedia.org/wiki/Sally_Clark