Paradoxica blood rage on kill not working when CWDT used in weapon

I've just equipped a paradoxica with 15% chance to gain blood rage on kill.
I don't get the blood rage buff if I put my CWDT in the sword. If I switch the CWDT to my shield then I get the buff.
Is this intended?

So the trigger blood rage on kill is actually like an invisible trigger on kill support? Can I socket other stuff to trigger on kill?

No. It only works for the Blood Rage

It's more like, there's an invisible Blood Rage skill on the weapon linked to an invisible Trigger on Kill gem. The trigger on kill can't affect anything other than the blood rage, but the blood rage can and will be affected by any support gems in the weapon. Useful with things like increased duration... not so useful if you want a different trigger skill in it.

THank you smart exiles :)