Sure, but you still need an explanation for what would have to be reversion to ancestral forms of an italic script.
There would have been a lot of refugees from the Punic disasters, and staying a long way from Roman centers would favor survival.
Being the only literate group in a wide area would explain the surrounding majority's adoption of a non-standard script, otherwise a mystery. Use of the script could be confined to ephemera indefinitely long before a change that led to its use to inscribe durable material, so a gap, while inconvenient for historians, is hardly disposative.
So yes, that date is only an upper bound. But there's a reason the scholars in this area believe what they do regarding the origins. For the type of cultural contact that can lead to the adoption of a writing system, that kind of closeness is important. You can't just handwave away a gap of several actual human generations, while at the same time ignoring the other major powers that are much closer and certainly exerting stronger cultural pressure than Carthage.