The article is brilliantly written to lead with the significance of such a find before providing evidence.
You might want this one: http://www.rollstonepigraphy.com/?p=921
> I will convey my own perspective regarding these four inscribed clay cylinders: namely, the script is Early Alphabetic (based on the clear morphology of the letters), the language is arguably Semitic, and the date is early (based on the secure archaeological context and carbon 14 dates).
> My initial thought (because of the graphemic shapes of the signs on the cylinders and the clear similarity to Early Alphabetic letters) was that these cylinders might be intrusive
So, the major argument that they're writing is that they look very similar to other writing that we can read. Imagine that you can read Latin, but not Greek, and you're confronted with some inscriptions in Greek. Should you call them writing?
Did they find a bunch of these artifacts, with a variety of inscriptions? If so then sure, I buy it. If it's just the "CHON" fragment - that could well be coincidence.
So if all of the handful of fragments have marks that look like actual alphabetic symbols that were actually used in that area (later), that's substantially stronger evidence than you're giving credit for.
Not sure if this is good example since we know that Greek alphabet really is writing.