With all due respect to your venerable number of posts, and likely, your knowledge of the game, and hours played, etc etc. I mean that. No sarcasm or disrespect intended whatsoever in this entire post. I say that only because context, tone, etc are lost with text. i don't want to come off as a jerk.
The short of it (TL;DR as the kids these day say).
Unless you have tested the save and gotten the weapon to proc, and you can post screens of the weapon's sheet showing 1 or more out of 15, you don't know with 100% certainty that I'm wrong. Really, you can't even say that it's likely to be the