Another way to think about it is if you have a portfolio that consists of both your assets (whose exposures and weightings you control) and your liabilities (which usually don’t control but which you need to understand), and then you are managing to maintain a surplus, or at least not a deficit.
Mathematically, this is more complex, but conceptually, it clarifies things a bit. Your portfolio can be thought of as being a short position in your liabilities, and then long positions (and shorts, if the IPS allows) in your assets. You then lower your risks by having assets that are negatively correlated with the short liabilities positions, but since a short position has the opposite correlation sign as a long position, it means that you are actually looking for assets that are highly positively correlated to the liability values. This is why it is a bit counterintuitive, because usually you are looking for negative correlation, but in this case, the fact that your liabilities are essentially shorts, means that you are looking for high positive correlations.