Jagex's bot watch is likely to be heuristic based. From what I understand, location is one of the many things they'd use to identify you as a bot. Other things could be IP, play duration, etc, but these are all assumptions. No one knows exactly what causes bans, and if someone does, it'd be kept secret anyway. Duel arena is also 'heavily' botted, as staking can be seen as a very profitable method, and it was also previously used to transfer / mule gp, so it's likely that this location is actually 'noted'.