I can bet my ass off, they have some super amazing script like facebook secretly got, with Analyzing different data, as play times, activities, chat %, TPS, Statistic, Gold Earned, etc etc.. Thats could make a clean in 5000 people reported to lets say 100-150 then the 100 150 gets manually inspected by blizzard's staff to validate botting, then ban.. I think they doesnt look what you do when you do it, but the result you got from your activities, and the result, is NEVER, absolutly NEVER hidded, you can't hide, its server-sided, currencies, items, char, all what you do is server sided, and its totally own of blizzard, so they can do whatever they want, they dont need to KGB-like introduce your computer to see what ur running..
After 12 Years they should have complete database of what each type of gamers is suppose to earn is a certain amount of times, like 16/day try hard can have up to 1x0000000 gold, up to 1 legs, up to... 10 Hours/day gamers... .. .. etc etc.. And all that shit together make big clean between false report and truth bot spotting..
Blizzard is rich now, they fairly can have team like Facebook/Google, they fairly can have that kind of analyzing script.. and it would explain the long calm period we have before hostilities..
Its sure this it how it dones, when i look at myself, i'm sure at 100% this is not a report, but its an addition of suspicious things i've done on my account for multiple times that could lead anyone to know that i'm botting..