[2021] Has the game gotten harder since a16?

Originally posted by AzureTerra: An oddity we have noticed is that we have a trench full of spikes and the zombies have a tendency to clear it of spikes before deciding to make for a wall ~ we'd expect them to come from a direction and make a way across but they get down in there and go around till its clear before making a breach somewhere.

This is not an oddity. Instead you have noticed the truth that zombies see spikes as regular blocks. The fact that they think they can run across them like a bridge or climb them like stairs can give you important strategic options.

For example, when you fill a trench with spikes they will always seek to run across what they view to be a bridge across the trench rather than descend down and then up the other side which is why they will empty a trench of all spikes first.

There are other layouts you can do if you think about how zombies see spikes...