Question Atlas variant with split

Hello.
I want to make a variant atlas with a scale of 0.5 and etc1+split alpha for android.
If master is also compressed with etc1+split alpha, then UIImage is automatically replaced from UI/Default to UI/defaultetc1 and _AlphaTex is passed to the material.
But ETC1 passes 2 times. Visually you can see the compression of the master Atlas affects the option. If the master atlas does not compress etc1+split alpha, then there is no alpha texture for the atlas variant.
I want a master atlas in rgba32 and a variant with a scale of 0.5 in which there will be alphatexture . How can this be achieved? There are a lot of such textures and it looks unrealistic to create alpha textures with your hand.

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The 2018.4. 3f1 release notes state "

• 2D Fixed ETC texture compression Split Alpha Channel not working for SpiteAtlas Variants. (1126070)

" but the above behavior is repeated on 2018.4. 3f1