” then why is the exact same formula used after the sun and moon are in place to describe each day? “
Because the are the same. The solar day was invented by man, not God.
“The solar day was invented by man, not God.”
That doesn’t make any sense at all. God created the sun and the earth, and set them in their orbits, setting the length of a day. God says in Genesis chapter one that a day is “evening and then morning”, which is exactly how the Hebrews measured days. Even to this day, Jews observe Sabbath starting at sundown for exactly this reason.
To think that God used that expression to mean something other than the “evening and morning” days that we are all familiar with is akin to saying that God is trying to deceive us, which is an absurdity.
I sometimes think that if God had written “and twenty fours hours later, was the next day”, some people would argue “well, hours to God don’t mean the same thing as hours to us”.