However, knowledge requires a knower and to know something you “observe” the object; knowledge of the object is based on something observed in the world, which is delivered through the senses to the brain. The brain structures the sense data into a knowable object. This suggests the knowledge that particles exist in all possible states was observed (otherwise how can it be known?). But to know all possible states an observer is needed but an observer only sees one state. Therefore, the proposition postulates something (observing all possible states) it then denies (observing only detects one possible state).
This fallacy is quite common. For example, you could think being told you have Parkinson’s somehow created the disease (or made it worse) in you: all possible states were rendered into the Parkinson's state when you became aware of the disease. But only knowledge of Parkinson’s was created in my mind when I was diagnosed. I had symptoms prior to the creation of the knowledge of Parkinson’s; so the observation had created nothing but knowledge.
This also applies to knowing the future; such knowledge is unknowable without observing the “future” in the present. But knowledge and observing are acts of thought and thoughts follow one another at intervals of fractions of a second. No thought can jump over the next thought and therefore we cannot skip our present thought to know the future. Also, this is why knowing all possible states is impossible: the thought “all possible states” misses all other possible thoughts and therefore fails to take into account “all possible states”.