This discussion reveals one of the best reasons for keeping everything in a single document. Long gone are the days when the length of a document was a significant problem, at least for us writers of fiction stuff. I once tried the one-document-per-chapter approach and soon learned to detest it, for purely practical reasons.

Also, be aware that Libre Office counts "wprds" a little differently than MS-Word does, and it generally results in a longer word count.