If the two core switches are connected through L3 interface, per vlan one access switch will have 2 uplinks to core and all other access switches will have only one uplink to core. The worst situation is: all other access switches uplink to one core switch and HSRP decide another core switch (sorry I should say router here) as active gateway. In this case, all traffic will go through that access switch with two uplinks. (Suppose no manipulation, but poor manipulation will make the worst case happen).
