Randomly getting hit through successful parry

[Samulai]

I noticed that sometimes, after you successfully parry an attack, the enemy goes to the stunned stance but you still take the damage. If the attack was the type to knock you off your feet (like some boss attacks) that happens to you as well. I tried find topics about this and all I found was people claiming it was the half-parry. I've been testing this on the darkwraiths near Farron Keep Perimeter bonfire for like an hour now and that just doesn't seem to be the case.
The half-parry doesn't open the parry window, only gives you the damage reduction and nullifies poise damage. I tested this by intentionally getting half-parries, but never was able to make enemies go to the stunned stance. I also tried to miss the timing just by a nanosecond, but it always resulted in half-parry, no riposte window.
Then I tested if the problem was the same we had in DS1, where attack coming from your right would connect with your body before hitting the parry hitbox on your left. No luck there, since you can reliably parry attacks from all angles without getting damage.
Then I went to just land regular parries and see if it just happened at random. And that's what seems to be the case. My timing didn't seem to affect anything, the damage just sometimes decided to come through.
I'm not sure if this has something to do with my fps. I do get solid 60, although it might drop to 30-40 depending on the area.
Does this happen to you too? Any idea if this a bug or intentional? Why would Fromsoft punish us for landing a parry?
I'm still at my first, blind, playthrough, so no spoilers. Thank you.

[Effusion]

I've been noticing this too. While I agree that it's not the half parry the damage I take does seem to be reduced and I haven't seen any poise damage/knockdown come through it. Have you tried testing it with a 100% physical shield? I was thinking it might be reducing the damage as if you had blocked.

[Samulai]

Originally posted by frzn:

Have you tried testing it with a 100% physical shield? I was thinking it might be reducing the damage as if you had blocked.

I went on and did, still taking damage from full-parries. Good idea, though.
EDIT: And I haven't seen any poise damage come through either. Just the knockdown.