Slackware and patches
Usually, the Slackware crew relies on upstream developers and avoids to add own patches. So it is very likely, that a bug like the one you described comes from upstream.
Xfce and patches
I have sent a couple of bug reports to the Xfce team in the past and both bugs were fixed rather quickly. So they really listen. Regarding the typo you found: It's 'only cosmetic', so it may not be put on top of the dev's priority list, on the other hand my guess would be, that it takes no real effort to fix it. Let's see...