Really, Wikipedia? Even then it says that the language of kusthia is similar to Chalit which I have been saying all along.
Here's from Britannica, hope it will put this debate to an end.
Bengali language -- Encyclopedia Britannica
Look, so many of our heritages have been hijacked by the big mouth Indians. It is only because we are weak at projecting ourselves internationally. This is why Nakshi Kantha, Muslin fabrics and Mango like things have become India origin. I will not be surprised if Brittanica says Jamdani and Dhakai Sarees and Rajshahi Silk Saree are Indian origin. Also, to outsiders, Bangladesh, India and Pakistan all together is regarded as Hindustan or India, which is not today's geographically constrained India.