Wouldn't the traffic pattern be similar to watching Netflix?
But aside from it, it should be very obvious: A) you are notified by the intellectual property holders that somebody is streaming pirated content, B) a specific customer or set of customers, who are not a known streaming service, are serving tens or hundrends of IPs with video and C) these customers do not have much activity during other times.
Plenty of people stream commentary to matches without showing the game itself, so that would flag as guilty too
In theory someone might rent a server and do the streaming directly to his viewers, without using a known platform. This would be a legitimate false positive as you describe. But this would be so expensive I doubt anyone would do it when the alternative is a free platform with built in community and monetisation tools.