Aye, I guessed as much(with the playtesting).
Black knights isnt what is bothering me, they are pretty much balanced already.
My main concern is the mountain of special rules the Spectral knights got, especially how they ignore so many of the core rules as in how they ignore any terrain of the board. While opponents maneuver around terrain, BAM, here comes a sledgehammer of(assuming you got 5 of spec knights) 15 S5 ignoring saves + 5 S4 attacks(plus the effects of a banner should you chose to give them one). I know they are base S4 and need to charge to get S5 but you'd have mess up very badly to fail to get the charge. Even Daemon players would stare in disbelief at this kind of power. Nevermind maneuvering, just hide them behind some terrain and watch how you will controll your opponents movement phase. With 2 of these units it will be a complete nightmare for your opponent, especially for armies who have to come to you. The armies that comes to mind first are Brets and WoC of which this unit will just laugh at they slaughter their way through them.
So in a nutshell, whats bothering me is;
Ignoring AS, maybe go with Armour piercing instead which would mean -3 AS on the charge(same as a charging Bret lance) and completely drop Ethersight as IMO is just plain broken.
In short, too much maneuverability.