Confusion.

Our professor said this in our class today. He said, “today, you would’ve finished the first and the second assignment.”

He expected use to get those two assignments done by the time he said that sentence. This is the context. Why did he use ‘would’ve’? He could have said, you probably have finished the first and second assignment. Did he use it to show politeness? Our professor is very polite and little shy. Please help.