Bangladeshi workers in F&B sector

I came back to Delhi recently after a 2y stay elsewhere and I have noticed this odd trend. In Khan Market, at places I used to frequent, I have suddenly noticed that the waiters now are mostly Bangladeshi. I get to know this because of their Bangla accent and very weird generic Indian names like Rahul, Raj etc. I have also seen a lot of other working class people who seem Bangladeshi but when I ask them (in Bangla) where they are from, 9/10 just say Assam. Is this a recent phenomenon? Or am I mistaken. P.S. I don’t mind if they are legal immigrants, of course, but somehow I doubt that may be the case