That's why folks will refer to the "oldest copy" and from that try to infer what the original date of of the original copy might have been. Sometimes the "original" was an oral tradition. The Bible itself gives several clues about "oral traditions". First, all of them made use of the Memory Palace method of memorization. Secondly, they all recommended using an Ark or a Garden as a structural reference. History can be structured in the mind using a genealogy ~ e.g. the generations of the Patriarchs, or the reigns of French Kings.
Fewer errors than are popularly imagined entered into the ancient texts. The Jews, as just one example, had groups dedicated to transcribing and reviewing transcriptions so that no mistakes were made.
Oh, I have no doubt they were literally copied, just would like to see one from that time, that exact time. May be there are none.
I have been told of recently discovered pottery fragments containing fragments of scriptures demonstrating examples of of ancient texts dating to perhaps 1,000 BC.
Ezra indeed. /s In Shemitta, I have a very thorough argument for why the scriptures could not have been written later than stated therein, as is commonly asserted in the scholarly community.