question about Roman military writers

[Robert Vermaat]

No ancient author survives in his own hand, meaning that even if a work might have survived all the opportunities for its destruction which rose in antiquity, if no-one was interested in taking the time and effort to copy it in the middle ages or renaissance (when there were, of course, no photocopiers, fax machines or scanners to make things simple or quick for the copyist), it would not have survived for us to be able to evaluate its merits for our purposes.

Which hits the nail on the head. The corpus of writing from Antiquity that survives today does not tell us anything about what was written or about what was not written. If anything, it tells us something about the tatses of those who came after, and why they chose to have something copied for posterity.