Texture with 1-bit alpha no longer an option?

DXT1 is supposed to have an optional 1-bit alpha for use as a cheap mask, but adding any alpha at all to my color map just results in DXT5 being used and jacking up the texture cost. Is the additional 1-bit alpha mask no longer available?

In material options we have “Masked” and “Translucent” blend mode, Masket seems like 1bit alpha mask in slot “opacity mask”, in masket mode we get HardEdge mask, what else could cause this than oneBitMask?

Changing the material’s blend mode doesn’t change the compression settings on the texture. You can still view the alpha as its own channel and see it is grayscale, not 1-bit.

Hello. Sorry for the necro, but I’m googling for 1-bit alpha in Unreal, and there are mostly unanswered threads like this one. I stumbled upon one with some info, though: dxt1 with 1-bit alpha - Rendering - Unreal Engine Forums