the idea of zombielink is more as a defense ie you get a chance to either kill zombies that are poised to attack due to the extra activation or just move out of the way just in time to save you and perhaps some fellow heroes too.
not really meant to open new buildings in the zombie phase
Even if it's not meant to be used to open buildings, it's still possible to draw activation cards while spawning a building normally, and therefore be able to move about unimpeded before any zombies appear. I feel the skill should probably be clarified to state that all spawns are resolved before the Zombie Link skill kicks in. It'd make more sense.