COUNTIF beaviour with dynamic arrays

Hi, can someone pls explain to me why the following first example works but the second one does not?

There's apparently restrictions in what Countif (countifs etc.) are willing to accept as a range argument:

Works:
A1 = UNIQUE(B1:B10)
C1 = COUNTIF(A1#,"*")

Does not work (i.e. combination into one formula):
D1 = COUNTIF(UNIQUE(B1:B10),"*")

As a further question: Why does UNIQUE output an empty cell as a Zero?
What would be a way to have UNIQUE show both empty cells and cells with a true zero as distinct unique outputs?
What UNIQUE does instead is output two Zeroes as distinct unique items.

Any help much appreciated.

Thanks and Regards