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.
Huh, I got the same result when using the Lemmy Explorer section and searching for an instance with “Exclude NSFW” selected. If I searched by community instead of instance, it worked and included the instances you mentioned. Weirdly it actually included at least one community that was NSFW with “Exclude NSFW” selected.
The feature works as expected for communities, for which it’s up to community moderators to label their communities as being NSFW or not. Maybe the community you found wasn’t set as NSFW for some reason?
Not sure how it’s set on a per-instance basis, but it definitely doesn’t seem particularly useful in its present form for filtering instances if most SFW communities are from instances counted as NSFW by the Lemmy Explorer filter. A small problem in relative terms, but still something I thought was worth making note of. 👍