Can't obtain the mushroom spore block

I'm in a survival achievement world and I wanted to use the mushroom spore block for a path I was making which weird I can figure out how to obtain. I have all variations of the mushroom block due to using my silk touch axe but I can't figure out how to get the variation of the block I need.

I read on Reddit people recommended putting other blocks onto and waiting for them to change but nothing happened.

Is this a bug or is it an unavailable block in survival?