Brent Ozar notes that estimated plans are not guarantees:
A reader posted a question for Office Hours:
Hi Brent, What is your take on Hugo Kornelis’s explanation of execution plan naming. As her his explanation, estimated exec plan is simply an execution plan whereas actual execution plan = execution plan+run-time stats. Do you agree that the naming is flawed and confusing? – Yourbiggestfan
Click through to see examples of when estimated plans might look different from actual plans.