Okay, I'm not sure if I'm 100% accurate but this is what I think:
Lets use MMC for the example. Say if you flagged reach with one 3.2 hit then yes the likelyhood is you will get banned after 2 weeks (or whenever they do ban waves.)
The reason why ban waves occur is because the Anti-Cheat needs some time to determine if someone is cheating. If someone went on MMC and autoclicked for like 6 seconds and logged off, it can't hand out a ban because it hasn't gathered enough information to determine if they're cheating or not.
So to answer your question in short, a ban wave is simply when the anti cheat bans several players at once because it is the time period where it has gathered enough information on players to be certain the bans aren't false.
It works differently for other modules i.e if your reach hits aren't consistent enough on mmc it won't ban instantly but it will ban wave. Not sure why this is but they must be doing something right lol.