Normally aggressive mobs towards Villagers will not pathfind to them if either are on a half slab

While doing some testing, I realized that zombies would not try to pathfind tomy villagers to make them zombified. A little testing later and I realized that the zombie would only pathfind if the villager was on the upper half of a slab and it itself was doing so as well. Not sure if this was already reported, but I couldn't find it anywhere.