does the current version of high sierra support apfs for fusion drives?

Only because Apple announced it would be replacing HFS+ with apfs. Had they not said a thing about it, those of us who have been patiently waiting for it wouldn't have inquired about it. Just a case of getting the cart wwwaaayyy out in front of the horse, which Apple used not to do.

They are replacing HFS+ with APFS, just not on rotational hard drives at the moment.

When they get it working as they wish on a rotational hard drive, they will likely continue the transition.

Whether you are running High Sierra on HFS+ or APFS is pretty much transparent to the user.

What great difference are you "patiently waiting" for?

No, HFS+ only.

No, it doesn't, but why does it matter?

Sartre would be proud.