Right, and if there was an unsolved murder at your next door neighbors, and your DNA was found on the murder weapon, it would look very bad for you.
Fortunately, investigations don't start by trying to prove that anyone without an alibi is the murderer, they start by finding the evidence at the scene, interviewing witnesses and identifying likely suspects, and then ruling them in or out, based on verifiable alibis.
In no way, IMO, does BK have a verifiable alibi that proves it was impossible for him to have committed this crime.
For perpetrators under a certain age, it would be highly unusual for their digital footprint, or absence of one, to not provide indicators as to where they were and were not.
(And I realize you are not arguing this either way, just giving an example of a real, but hard to verify alibi.)