I think this picture could help you. What you are seeing is a 2015 Giant Fastroad standing next to a 2002 Jamis Tangier. Please note the garage door and the lines in the door. Then note the handlebar and seat heights. I adjusted the Jamis 13 years ago. I adjusted the new Giant last week.

The moral to the story is the frame size gets you in the ballpark but you are still going to need to adjust many things before your bike will feel right.

If you look at this picture carefully you may never realize these two bikes are within one inch on every dimension I have measured.