I’ve got one other idea. But it’s not really an idea of it necessarily will help Mike, but it is that the Israelites actually did believe the creation was finished and complete. Much in the same way that you glean from passages like Jeremiah 31:35 where the heavens were perfect and fixed.
And lo and behold Tycho Brahe’s supernova in 1572 caused a stir as he himself was in disbelief as everybody just knew that creation was done. So in this sense, the Israelites were using the best knowledge of their day to tell their story and God didn’t give them any supernatural knowledge that he was still creating her things were still being created - instead speaking to them in for familiar terms and familiar knowledge of their era.
Also, the point earlier about other creation myths including the fact that the gods rested bears large witness to the scriptural account because it explains why the Genesis writer felt compelled to have Yahweh rest and the end of our story. It’s just what the gods did when they were done with it all (culminating in man).