In bn_BD [1] locale it says,
-----------------------
LC_COLLATE
% TODO: Bengali sorting should be added
copy "iso14651_t1"
END LC_COLLATE
-----------------------
In bn_IN [2] locale it says,
-----------------------
LC_COLLATE
% Copy the template from ISO/IEC 14651
copy "iso14651_t1"
%
END LC_COLLATE
-----------------------
I don't see any difference in the LC_COLLATE block, except the % comment
line. :-?
What you need to fix are the collation rules specific to Bengali and,
of course, this must be done in both locales as I suspect that the way
to sort things does not depend on the country, hopefully..:-)