Not silly, that’s a common cleaning technique from janitor/cleaning staff i was told a while back. Use a little bit of what causes the stain/gunk and it helps break down the bonds by binding with the already-solidified object and trying to mix with it, weakening/changing the concentration of the ‘stuck’ substance
I think therea a lot of little racism along the way that inadvertently affected whites as the middle class dwindled and the number of poor whites increased.
So, all rooted in racism, maintained by classism, I’d say.