This is a continuation of my previous post.
At the time I'm writing this article
there are 2 comments showing publicly,
but including private comments there are 12 total—
I've received quite a lot of feedback
(even if you don't select the private option when commenting,
my settings make the content private anyway).
Thank you so much.
Among them, many comments correctly identified
what I'm currently thinking might be the culprit.
I forgot to mention this in the article,
but the flux (hydrochloric acid) I use for
soldering cable connections didn't strip the anodizing either.
So that's the thing—if it's not an acid...
It's something we don't normally stock at the shop,
so testing will take a bit of time, but I will run the experiment.

Also, based on the wear pattern of the nipple color at a certain angle
and the fact that liquid is dripping from the rim side down through
the gap between the bead hook and tire,
the length of time the wheel sat stationary is definitely a factor.
There's a possibility that if I had rinsed thoroughly right away
after using it as a cleaner and dried it well,
it would have been fine.
But considering that even a small oversight—
incomplete rinsing or forgetting to wipe—could cause
an irreversible change to the aluminum surface,
it's too risky, and honestly I wouldn't use it.