Yes, that is correct. See here: http://www.gtaa.com/en/travellers/connecting/connection_tips/
I tried to paste in the relevant bits from this page, but it's not pretty - lost the formatting. Note I DID edit the pasted bits to remove some non-relevant items, so you should check the link for the real page to see more details.
Transiting through Canada Border Services Agency between Connecting Flights
When connecting flights at Toronto Pearson, you may be required to transit through Canada Border Services Agency (CBSA) or U.S. Customs and Border Protection (CBP). Refer to the table below for specific details about your flight.
Connection Customs Required
U.S. flight to International flight Canada Border Services Agency
International flight to U.S. flight Canada Border Services Agency*** &
U.S. Customs and Border Protection
International flight to International flight Canada Border Services Agency
- Domestic flights are flights within Canada.
** Canada Border Services Agency combines the processes of Canada Customs, Citizenship and Immigration Canada, and Canada Food Inspection Services.
*** Some International to U.S. connecting flights at Terminal 1 do not require passengers to clear CBSA before clearing U.S. CBP inspection."
But it's not really that bad. You don't have to wrestle your checked bags very far (assuming you aren't a RS carry-on adherent). It is an extra step, but as many Americans forget (my own parents included, both of whom have Ph.D.s), Canada is truly a separate country, so it's logical to have border control here.