Even when specifying a font and font size, students still mess with the margins and bump up the size of periods to meet their page requirements. Same thing with a word range – students will create verbose sentences to meet the requirements. My favorite prof in college flipped it – she had a page maximum. She readily told students it could be as short as they wanted, as long as you fully responded to the assignment. New students were thrilled. Smart students knew that to fully answer the assignment, it would take all four pages.
For a tutorial class I ran I gave my students the precise margins, font, and font size. I wanted exactly one page double spaced, so they could write 23-25 lines. I was specific because I only got paid for one hour of grading per student, and as there were 4 assignments I wanted to have my marking down to a science. I didn’t get paid enough to turn pages! After the first assignment was due, I had to spend some time in class showing undergrads 5-8 years younger than me how to set this up in Word. That was the most shocking part for me.