That's not to say, Veronica, that you can't start filling in the appropriate GSCC forms and gathering the appropriate documents for registration now. But you can't send off your registration pack until you have graduated and have proof of the MSW certificate and transcripts and you are sure you meet the 130 day requirement, as per all the stuff outlined in the link. It is only the GSCC that can clarify what you need to do regarding registration, not the agencies.
The agencies don't know the ins and outs necessarily of registering with the GSCC if you are a foreign qualified social worker. All they know is, if you have GSCC registration, they can place you and get their commission. Hence the push. They don't care if you won't meet the requirements - it wouldn't be them losing out on the registration fee, but you would be. I'd contact them only after you receive GSCC registration really.
Hope that clarifies further. Good luck!