Is your thesis that writing was invented much earlier than presently believed but also it was only used to make marks that were easily destroyed and never incrementally improved so it would seem like they had no prior experience ?
But like the article says even if you never deliberately bake the clay tablets, accidents will do so anyway.
It's easy to imagine we don't have the first year of writing, maybe the first human lifetime of writing, but it stretches imagination to invoke a situation where somehow a civilisation is writing clay tablets for hundreds of years, decides they are not to be made into permanent records and somehow they're so lucky that there's never a house fire, a goof at the bakery, somebody's kid spills hot stuff on the tablet, nothing like that and so over that period every single tablet is destroyed/ erased as expected and leaves no trace.
If they ever used clay to begin with. Did all civilizations that independently developed writing start with clay? I don’t think the mezoamericans used clay tablets and it seems that vegetable fibre was the preferred medium for all others that had access to it.