Seems like a stretch to me to think about it this way.
No complaints about this in 8 years makes me think there is no issue at all here.
If admins want ot use this theme but are unsatisfied with the background pattern, they’re free to change it (but I guess you’re talking purely from a user perspective?).
So you’re not technically wrong, this is a traditional Japanese pattern called Sayagata, which is consists of interlocking manji which is the Japanese word for swastika, but it’s the pre-nazi Buddhist sort.
That said, now that you’ve pointed it out I feel like it should probably be replaced to avoid negative connotations. Fortunately there’s another Japanese pattern from the same source that makes for a nice replacement, https://www.toptal.com/designers/subtlepatterns/japanese-asanoha/