Tire size is regulated for all brands. A 205/55/16 Dunlop SP-9000 (around $200 a piece) is exactly the same size as a General Ameri*AS 205/55/16 (about $70 per tire) Tread pattern and depth are the only difference, making one seem a little wider (because of tread design and depth) Tire size is also measured once the tire is mounted and inflated on a rim. Again, a General tire may indeed look thinner than a Dunlop simply because of the quality of the compound on the Dunlop is better and stronger, making the tire conserve it's size characteristics compared to the General's cheap construction.
