When viewing the instance list in Lemmy Explorer, enabling the Hide NSFW option hides 490 of the 567 listed instances. On the reduced list of 77 instances, feddit.cl, feddit.uk, and aussie.zone are listed as the largest SFW instances.

Unless I’m misunderstanding how the NSFW instance sorting function works, it seems to be a mistake for so many instances, including lemmy.world, lemm.ee, and most other major instances, to be categorized as NSFW.