Certainly you've given no good reason for anyone to buy your "seventh day" song and dance.
Aside from there being no declaration of the seventh day having ended, you are correct. But, if Moses was the writer, recall that he claimed in Deuteronomy 32:4 that all God's ways are perfect. Since God proclaimed each of the first 6 days as 'good' upon there completion, there does not seem a way, IMO, for God to have made a similar proclamation at the end of the seventh. That is, not yet.