i suspect due to the amount of locations, the game has to spread them out more in the initial spawning phase; the 28days until peak.
the amount is still growing
also, dont feel to safe, i finally got the night sprinter mod to work the way i wanted it to work.
10% of the Z's become sprinters at night now.
enjoy the lower pop as long as you can!
I'll give this a shot when I come back home from work. I thought of a silly idea, if your suggestion doesn't work I think I'll try having the item spawn as super hot, and have it hot enough to finish cooking by the time it cools down haha. When the item is crafted by the player I'll override the static controls to make it normal temperature. I just don't know the heat mechanics of the game so I'm brainstorming here.
Additional speed modifiers for slow and fast shamblers and even for sprinters, modifiers for % of zombies being each type and modifiers for zombies loudness (groans and movement). There are some mods for that but these would be great as some extra features in sandbox.