If ordered executed correctly, you should have the option between using a qualifying date of the date of order (on your POC) or date of delivery (date you actually financially purchase the vehicle). 99% of rebates are lockable and would work in this method.
However, there are a thousand ways to get burned, so many dealers - will instead say "whatever it is when it shows up" and I don't blame them. Sometimes the customer mis-understands something, other times Ram makes it complicated, etc.
What DEFINITELY does not work, is a random date in between.
Lets say you order 11/5, you've got a $4K national rebate on a tungsten.
In december, they do a Merry Christmas Tungsten $6K Rebate
Then you receive on 2/14 and there's a "Happy valentines Day $5K rebate).
You choose between 11/5 and 2/14. You do not get Christmas