Well, he said after. If it was the same time as the other accounts were being botted, I would fully agree with what you just said.
Flagging IPs doesn't make sense in terms of resource usage. If you continue to monitor an IP that's had bans in the past, you'll be wasting your time if they stop botting.
There is extreme cases when IPs are flagged, lets say you make 500 accounts a day and they're all constantly getting banned. Yeah, that IP will get flagged. Because it's an extreme case and it makes sense. With regular gold farms that are not run in the worst possible way, IP flagging does not make sense.
I continue to believe that it is not a problem anybody will face if they are botting.