I think that's probably just because it's been revised and the placeholders were added after.

To be fair, it only adds an extra 18 chars, taking it up to 238-byte in size.

EDIT Here it is once you add the extra property:

    (o=b=>{for(j in a)for(i in a)y=a[i]+-~j,b?document.write([["<p>"][i]]+"<input onfocus=value=[o[id]] onblur=o[id]=value;o() id="+y+" placeholder="+y+">"):eval(y+(".value"+o[y]).replace(/[A-Z]\d/g," +$&.value"))})(a="ABCD")