By that specific notion, any hash where you can shave a hair of complexity off the first round (e.g. via SAT) is insecure, because it takes ever-so-slightly less effort to brute force it that way than pure brute force. Adding more rounds doesn't change that.
Sure if you want to be pedantic. However even if you double the number of rounds, the number of operations required to brute force increases by only a factor of 2. Since the number of operations is likely to be a very large number already, such a change is insignificant and we can consider the brute force cost to be independent of the number of rounds which is usually a small integer.
