That does suggest (with big flashing signs) that he is hiding a shaved head there, but... For me, I'm not convinced it's not just Snyder suggesting Eisenberg wears hats to prank the fans and keep us confused.
Not that he's hiding, it
is shaved. Look at the sides, it's clearly a buzzcut.
But there's another thing I am somewhat curious about. And I have a little theory.
On set photos where he was wearing that scarf on his head, it could be clearly seen that he had hair underneath, whether it was his real one or a wig. Wearing both a wig and a scarf seems a bit excessive, right? It could be that he'll have a hair in a film at first, but will shave it off or lose it later in the film (or take off a wig and throw it at Superman

... oh Zryson, sometimes I almost miss you).
Now hiding the fact he's bald makes no sense, everyone expected him to be. Besides, it should've been clear to Snyder and everyone else that we'll figure out that his head was shaved for the role once we get to see him with very short hairstyle (with which he was never seen before, as far as I can tell).
But if he was indeed meant to have his hair at some point in the film and lose it at another, keeping that hidden makes sense, as it would otherwise give us a clue about the chronology of the scenes.