I know this is a quite old post and for UE4.
I am using UE5 and had the same problem.
Now I found that the problem is because the Editor will not reload the ini file until it is restarted.
I am not sure whether this is also your situation, but for me, I restarted the editor, the property is read from the ini file.
Also, in the editor, use GetIni console command, I can confirm what value is in the current editor memory, also can confirm whether it is loaded.
It is documented here: Configuration Files in Unreal Engine | Unreal Engine 5.4 Documentation | Epic Developer Community
I hope this could help someone like me, who spend plenty of time to find out the solution without restarting the editor.