When you ordered or paid for a product has no relationship to how, when, or if you used it. The only meaningful date for submission of a tax return is provided within the e-mail you got indicating your submission was accepted by IRS and/or State ...
"For my 2017 tax return, my order date in Turbotax is 4/17/2018, but the date Turbotax received my federal and state return is 5/11/2018. Why did this happen?"
What does that mean "date TurboTax received my Federal and state return is 5/11/2018." I don't understand what you mean by TurboTax "received" the returns.