Chen Celerity does not proc on killing blow

Chen’s lvl 16 talent CELERITY:

Basic Attacks against Stunned, Rooted or Slowed enemy Heroes reduce the cooldown of stagger by 2 seconds and grant Chen 30 Armor for 3 seconds.

does not proc either component when delivering a killing blow onto a slowed target (i’ve only managed to confirm this with the slow from chen’s own W abilities but ive noticed it happen in regular games on various CCed targets)

This means if stagger is on cooldown, and you kill a SLOWED (or presumably stunned or rooted as well) ENEMY HERO with an AA,
1.You do not gain 30 armor, or if u already have 30 armor from a previous hit it is not refreshed.
2.You do not get 2 seconds of stagger CDR

There is 0 reason delivering a finishing blow to a valid target should not proc an on-hit effect like this. See my previous post about pre-rework cassia, this type of problem popped up elsewhere in the past and probably still affects some other heroes althoough i cant recall off the top of my head.

I did test several other on-hit and CC-conditional (“executioner” type) effects and at least the following worked fine on killing blows:
Anubarak executioner
Anubarak lvl16 beetle juiced “counter” increment
Greymane executioner
Sgt Hammer executioner
Sgt Hammer lvl7 spider mine CDR
Muradin executioner
Muradin Q CDR
Muradin W and E CDR from lvl 20 avatar
Alarak mocking strikes both 1.5s CDR and doubled CDR

Getting that additional 2 second stagger CDR can mean the difference between life and death for chen since it makes you temporarily unkillable, so this does significantly impact his gameplay, not to mention the armor.