Well, the only thing I can think of is that maybe it has more than one node (my mouse has keyboard and mice nodes because it's programmable, for example). Honestly, at this point, it's become too much hassle. The time spent trying to do this even remotely elegantly is not worth the few minutes it would take to learn how to remove a laptop keyboard and following @Lord Boltar
Lord Boltar said:
Another option is to take it apart and unplug the keyboard ribbon cable - of course that is more of a permanent solution
because the keyboard is stuffed anyway. You're not losing functionality. And disconnecting the cable is simple, but if you need a QED, here's a video I found with a ~1min search:
(Lol, I think that dude's at work!!)
To keep the video, grab youtube-dl (the latest version, not from the repos).
Also, if you want to replace it, I found this:
I'm sure there's somewhere in your region. If not, your OEM may still stock them. Personally, I wouldn't spend the cash unless I had to, but if you travel with it a lot, then it may be a thought.
Anyway, that's what I would do. My policy is keeping it simple and right now you'll spend 5 minutes disconnecting that keyboard as opposed to the 5 days you've spent trying to disable it so far.