Ment "biter movement speed reduction of ~30%" by any biter-changing mod.
The reason is that it gives a more classic rts gameplay, when the players\commanders have the time to: 1. Spot a wave\group 2.React\Regroup\Manoeuver their "armies"
For exemple, in rempant fixed - there are biter movement speed settings =)
If you're fine with vanilla biter speeds - no need to change anything.
Will see if i can add an optionnal biter movement speed somewhere (without breaking anything)