Yeah it can be jarring. But I will say that fanbox and etc has, at least anecdotally, helped some artists get some extra income. Especially those that aren't as prolific or ones that can't get published in other countries.
Although there are other artists that have taken to it as a more direct means monetizing what would formerly be considered "filler art" in more comprehensive SFW and 18+ volumes. Or in some cases the "more of the same, but naked" patreon artists.
Not sure where this particular artist lands, since I generally only know their "FPS de Shosi..." title.