This is something you need to ask the International Office, not us here. It seems something has changed within BCIT's International Office recently. Maybe a student got in trouble so the International Office revised procedures. Maybe IRCC told them to do things differently.
Regardless, without knowing why your international office has made everyone request letters for co-op work permits, none of us here can tell you what's going on.
Regardless, without knowing why your international office has made everyone request letters for co-op work permits, none of us here can tell you what's going on.