You CAN get it:
https://forums.spongepowered.org/t/how-to-get-block-variant
And for non-blocks:
https://forums.spongepowered.org/t/finding-the-variant-of-non-block-itemtype
But I agree with @dualspiral that you probably don’t want to (and the method I used there might not be supported for much longer). Only reason I did it that way was because of the way my plugin is set up.