None of which proves the statement is not true. But at least you didn't succumb to making up an elaborate lie such as claiming that someone actually denied the event took place.
Those are however good points as to why the defense would not make the claim in court.
Your understanding is correct. The early press report was that the DNA was found on the tip. Presumably, Raffaele had seen this report before making the entry in his diary. I don't think we have been told exactly where the DNA was found but in at least one image of the knife you can see the long rubbing marks that Stefanoni refers to near the middle of the blade.
First of all, what is a lie? From
wikipedia we can find:
"To lie is to state something that one knows to be false or that one does not honestly believe to be true with the intention that a person will take it for the truth." Since we are only talking about something that Raffaele wrote in a private diary, there isn't a second party to be lied to.
When we find evidence that the statement was intended to be presented as a defense I'll look for evidence that supports or refutes it. Until then, it isn't even an issue.