Well, not exactly. They sometimes build the sets at up to 3/4 scale smaller to save money and space. Even use an actor that is smaller to sit inside it and walk in front. I'm not certain that was done in this case though. But the TIE fighter set used in ANH had a forced perspective built in. So right there the model compared to the set was off.
I'd be super curious to find out how much of it they built. I think they used at least a portion of the blueprints to build the fins behind the cockpit.
(from production showing the set before the bluescreen was replaced)
looking at the blueprints the fins look a lot wider than they do in the image above but that could be a perspective distortion... I might have to build a mockup to see.
(just to be pedantic, I'm not sure there was a forced perspective in the TIE cockpit.. that set is fully 8-feet wide I think, they built it to the specs printed in the Rinzler book. Though you only really see the back wall of it there are extant behind the scenes photos of the full cockpit... it's frankly huge.)
I’m constructing a quick mock-up in sketchup and I think they actually did use these blueprints to build what we see. If I move the camera right in front of the pilot I can make the fins and cockpit parts match up nicely. I’ll post a render soon to show it.
I’m willing to bet they built it from the cockpit back toward the fins, similar to the x wing builds for filming cockpit scenes. I’d love to see something surface!