I'm not arguing with you but the fact remains that unlike SQLite, Access doesn't lock the database file so that only one user can write at a particular moment,

I'm not arguing with you but the fact remains that unlike SQLite, Access doesn't lock the database file so that only one user can write at a particular moment, it's more granular than that. It's also the fact that this worked very well for databases on small cabled LANs where no more than a dozen-ish computers might be interacting with the database at any one time. It was never designed for use over the internet (having said which I have maintained a forum running an Access mdb file as its backend since forever without a hitch the forum software process does the database edits so it's like a database server process in a way I suppose).