Forward rendering and msaa x8 with opacity mask (4.21.2)

Hello!

I’m not sure it’s a bug or not, but the msaa x8 works kinda weird.

msaa x2 and x4 is also has problem like weaken opacity with opaciy mask material, but x8 is acting just like translucent.

I’ve research some, and I guess this problem comes with alphatocoverage (i’m not sure)

I wonder anyone bumped this problem? and is there any solution to fix?