Title says it. In a public instance of a world, it appears that LocalPlayer.isInstanceOwner is showing as false on the user who uploaded.
According to multiple staff (notably PhaseDragon confirming this expectation multiple times in discord), the VRCPlayerAPI.isInstanceOwner _should_ be true for the world uploader for any public instance.
Here is a recording showing the behaviour: https://streamable.com/mgfgso
My authoring account should be able to see the lock icon when LocalPlayer.isInstanceOwner is true, but it never is set to true.