[Two Side Foliage Shading] Opacity has no effect

Hey folks,

when i try to create a simple “Two Sided Foliage” Shading Model with opacity, then has the opacity no effect. I try it with a scalar, mask or texcoord mask nothing works.

The UE4 documentation say, it works stand (ue4 4.9):
https://docs.unrealengine.com/Images/Engine/Rendering/Materials/HowTo/Subsurface_Scattering/SSM_Masked_Texture.jpg

My setup:

https://forums.unrealengine.com/filedata/fetch?filedataid=170646&type=thumb

BlankScene, tried with ue4: 4.15; 4.19; 4.22

Can anybody confirm this?