Brotherin, it would be your reading skills that should be wondered about as the scan clearly says "Kakashi's arm becomes a famous blade that can cut through anything" IN ADDITION to the statement that it cuts through lightning.
sure, I'm not using that event as positive evidence for the notion that a TBB would damage madara's susanoo, but I'm saying that it's not good evidence for the opposite either.
no doubt, however we are given limits and durability feats for weaker susanoos, so it is possible to make educated conclusions based on where the current evidence leads us.
Itachi doesn't have perfect susanoo.... he has armored susanoo, perfect susanoo is the one that stands taller than 100% Kurama, throws out bijuudama-level destruction with just swipes of its sword and has a penis nose.
And his yaata doesn't get its no limits statement, I can agree that it's far more durable than armored susanoo's armored layer, but nothing in this manga except for space/time gets no-limits offense and defensive properties.
totsuka has only shown the ability to seal things with souls and things that it pierces, not side-slashes.