You trample the ground. Grass paths provide an optional speed bonus!
If heavyarmor is installed, it will generate them more frequently.
Disable speed on grass path blocks by setting $speedpaths$ in np.global to 0 (1 is default):
/scoreboard players set $speedpaths$ np.global 0
Current file for Minecraft 1.14/1.15
1.13 (unsupported), 1.14/1.15 (stable) and possibly for even later versions on the master branch.
This is the 1.14/1.15 branch. Switch branches to get to the respective versions.
Performance Impact 🔴2/5