Adding NPC's to the world and changing the config to have them show up on tablist works fine, but they are not shows in-order from A-z.
Is this intentional? If it isn't, can it be fixed?
I would recommend just ... not having them show up on the tablist.
The option is only there as a temporary measure until some issues are fixed.
If you're trying to fake there being players online, that's a good way to get blacklisted by Mojang.