I agree that filtration won't split a compound.
But look at the sentence I am talking about, it says "when elements make a compound through a physical process such as filtration or boiling, it is impossible to separate them."
Look at the English.
It speaks of elements making a compound through the physical process of filtration.
Can you not see it is saying that when you read the words it says?!
If it had said "when elements make a compound, THEN a physical process such as filtration or boiling, won't separate it." Then that'd be another matter that'd be fine but it doesn't say that.