What is a purpose of TextureGroup MinLODSize setting ?

Hi all,

a little background…
I use Unreal Engine 4.14 on Windows.
I’m working on a PC game that uses a lot of high res textures ( most of them are 4kx4k )
There are some that are 1k though. The game uses texture streaming. I need to give users an option to choose texture quality ( low, medium,high )
For that I use documented scalability features e.g.

r.Streaming.PoolSize
r.Streaming.MipBias

it works pretty much ok.

The problem is few textures are too low quality in low setting - mainly the 1k ones.
I read about TextureGroup and tried to change the setting for TextureGroup_Character - one of the textures of that group is 1k :

[/Script/Engine.TextureLODSettings]
 @TextureLODGroups=Group
+TextureLODGroups=(Group=TEXTUREGROUP_Character,MinLODSize=512,MaxLODSize=1024,LODBias=0,MinMagFilter=aniso,MipFilter=point,MipGenSettings=TMGS_SimpleAverage)

From what I anticipated the MinLODSize of 512 should be the actual smallest mipmap generated, am I wrong ?
The effect is that when I change r.Streaming.MipBias to say 6, all the textures from the TextureGroup_Character ( and any other group for that matter) are showing a really small mipmap
The only thing that works in my case is to tick the “Never Stream” option in Texture itself.

What is the purpose of MinLodSize then ?

Thanks a lot