There are of course many Christians who think an ordinance has to be equivalent to what it memorializes. So, if God worked six days and rested one day as a pattern for the Sabbath, the days are the same whether ours or God’s, and the rest is the same whether ours or God’s. Likewise, if Jesus tells us to eat the Lord’s supper because “this is my body”, then for it to be meaningful it has to be real flesh and not bread.
But as I’m sure you know, not all Christians agree. Many think the Lord’s supper can have real meaning even without the bread literally becoming Christ’s flesh. Many think the Sabbath can have real value for humans without it corresponding one-to-one with God’s own rest. The suggestion in Hebrews 4 that God’s rest – the seventh day – continues, and we are still called to enter it, suggests there may be something more profound in the seventh day than a time of divine refreshment and breath-catching after strenuous labour (Exod. 31:17).
The portrayal of God as a human labourer in Genesis 1 also suggests we shouldn’t expect this picture to reveal the mechanics or timetable of how God works. Each day, the account describes God working only during the day. After each day of creation, the narrator tells us that evening comes, then morning comes, with no creative work during this span. The refrain “there was evening and there was morning” does not define a day – it describes the uneventful passing of a night. So the whole picture of God working six days with the nights off, then resting on the seventh, makes sense as an anthropomorphic picture of God.
God is described this way, not because God really does sleep at night and take Sabbaths off, but because this gives humans a template for their own work and rest. And the structure of a literal week can indeed help us remember our creatureliness, just as certainly as bread can unite us as Christ’s body who partake together, discerning his presence among us as we await the feast to come.