Knockback damage for bosses

I dont know if this has been brought up previously, but is there a minimum damage cap before you can start knockback bosses and pin effectively.

In this case, this only applies to some bosses like papulatus and leviathan where you have to deal a certain amount of damage to be able to knockback.

This does not apply to some bosses like:-
Anego
Kachuu Musha
Bigfoot

Can anyone confirm whether this apply to all bosses and if no, why is it apply to some bosses and not all?

 

Lf> feedback on this

 

Gonna try with lvl 10 wep see if it still knockback lol

 

But im quite certain for papulatus and leviathan you need to deal some dmg to knockback it.