Yea, interestingly the two calculators give different answers for the same situation:
In both cases, the calculator puts great weight on the amount of shared space, where all four of the roommates pay equally. If I repeat the example posted here while specifying 'huge' shared space, then the cost-per person becomes even closer:
And to your point about one person being in charge and deciding, this is ideal, but often requires some level of financial stability for the primary renter, which might not be the case for new kids starting college.