Why are terracotta roads significantly slower than cobblestone roads?

[Wesley]

When I unlocked the city and the third-level cobblestone road,
I observed that the villagers slowed down significantly after walking from the cobblestone
road to the terracotta road,
and then accelerated again after returning from the terracotta road to the cobblestone road.

Is the game intentional designed that the roads become slower as they are upgraded?