i think the difference is that you was approved in the same time as your interview, and i am not !! i thing i was on administrative checking, but fortunatly i passed it fast enough. that is why i still do not see any changes online also, in your case they told that withing 18 months you will get GC, in my case it "several months", i thing this can be interepted in way as 18 months or in other way ... they writng letters by using the same template with minor changes ....