Masalipattam was another center for products that were produced around that region and not Bengal. Bengal had the Chittagong Port where even Ibn Batuta anchored and visited Sylhet.Yes you are spot on.. thats where the cotton was from....
You can read some good books on muslin like
1. From Muslin To Museum: The Rise and Fall of Bengal’s Textile Empire
2. Muslin
Also go through the books of eminent historians like RC Mazumdar. All had a view that Masulipatam was the town where muslin was traded with Romans and Romans only gave the name.
Bengal had a direct link to the Mosul Port of Iraq where the traders of the three Continents gathered to sell and buy. How can it be that products loaded in Ctg. will go to South India when the boats were traveling to the Persian Gulf countries including Mosul. Among all the Muslins produced in Hindustan the product of Bengal was most famous. Even some foreign traders used to call it Daka Muslin.