Plebiscite was forced on Sylhet people. Lord Mountbatten wanted Partition of Kashmir, not Bengal. See 1947 India in Wikipedia click here
Clearly written , it was SP Mukherjee who urged Hindu population of Sylhet to move in Cachhar, Tripura, Assam & NEFA(NE India was known by NEFA till 1950). This made Muslims majority in Sylhet & thus Sylhet referendum happened.
SP...
more... Mukherjee also did a blunder by taking part in Muslim League enforced illegal Plebiscite on Kolkata, which he lost. 1946 Returned in Kolkata & once again Gopal Pathha, Boro Gopal & Ranochandi saved people of Kolkata. They brought down Kolkata Muslim League HQ. But WB lost Jessore, Khulna, Barisal & Half of Dinajpur to East Pakistan to save Kolkata.