Yes, but the point is that there was no drug 'warning' for Civ4. So either the regulators are getting stricter about those things, Take2 is taking less chances, or there is more representation for drugs in Civ5 than there was in Civ4.
Given the recent furor in Australia about a particular violent game facing bans not because of the violent depictions, but because it also depicted the injection of morphine to represent field medicine treatment, I imagine game producers have become a little more aware of drug references than before.