It does not make sense. Many people complain about this.

I imagine they made this, so people would not complain about not finding their own games. But this can be solved by other means. Like activating the option, after uploading/updating a nsfw game. And not by locking that option.

There could even be a dialogue after uploading/updating a nsfw game that shows that option and reminds people that it is turned off. In big bold letters. Before they hit update/publish.

Just locking the option is about the most user unfriendly solution for this. Make sure to also use the suggestion box and tell Itch in the designated channel how you feel about the current lack of options.