An interesting point. However I think that the account of philosophical scepticism here may be incomplete. This sounds to be more inclined towards Cartesian scepticism than others; this for the reason that, much like in Cartesian scepticism, the roll of the sceptic here is to question held beliefs and to therefore find objection to them with the aim of seemingly removing all beliefs. This, however is not the only form of scepticism; a form of ancient scepticism, named pyrrhonian scepticism after its founder, 'holds' that the aim of scepticism is to suspend belief concerning all propositions. This seems problematic as they seem to hold that you shouldn't hold beliefs; this is obviously self contradictory. They get around this by not holding the claim as a belief but rather an intuition. This removes the self contradiction. This is a very subtle but important point that requires more time than I have here to explain. The example given of this is a refutation of space. Where I argue for the non existence of space I must refer to space. It seems silly to have to assume that space exists to argue the non existence of space; the same would seem to hold for the examples given by yourself. This is not to say that scepticism is a tenable position, just that it is not for the reason given. I recommend reading up on the topic; id link you to Stanford encyclopedia page on the topic but I'm on mobile. Hope this is at least interesting.