Welcome to the real world of applying for jobs (not just IB). To make an analogy to college applications, job hiring is like rolling admission where a decision can come any (not predictable to the applicant) time after you complete the application (interview) process, but with a very short (week or two) timeline to accept or decline an offer (like ED) if you actually do get an offer.
It is not like college applications where all of the colleges agree that the admitted applicant has until a commonly agreed date to decide.