That's true but if you go through that process you're kind of stuck going through US customs and can't hand your stuff to someone. I'm not sure what your options are in that situation precisely. I'm not sure if you can turn around and go back downstairs through Canadian Immigration and Customs or if you must go through US customs. Once you're through US customs you can exit through Canadian customs then go back in through US customs but that would be a real pain.

If you short check it the bags should come out on the regular carousel after Canadian Immigration. Then you go out through Canadian customs into the land-side area where you can hand off his stuff to his friend. Then you go back in through US customs as if you're just leaving Toronto on a YYZ-US flight.

Make sure what you're doing is kosher for entering Canada though. They specifically ask about commercial samples in the Canadian declaration. I don't know what the customs issues would be for that.

Also, the last time I went through YYZ on a connection to the US the line-up to get through US customs was ridiculous. And it was longer for people entering at YYZ. The connections line merged at the beginning of the maze but the originating line had another 100ft or more of line-up before that point -- I couldn't see the beginning of the line which snaked around the corner out of sight. So make sure you leave at least 60-90min *after* the point where you hand off your goods. You probably want about 3hrs total for this connection to allow for waiting for your bags plus going through both immigration queues.