Disagree with this. Pearson terminal 1 has had check through luggage for several months now. Your bag will check through from Windsor all the way to Orlando. You will need to wait before being allowed to clear US customs while the bags from your domestic flight are processed. Once called forward, US Customs will show you a photo of your bag taken as it cleared through elsewhere in the terminal and ask you to identify it. Presumably if their baggage scanners note something of interest there will be further processing, otherwise you will proceed to boarding. This is only applicable to AC at T1, other airlines out of T3 still use the old baggage claim and clear procedure.
There is a guide to the procedure on the Pearson site.
http://www.torontopearson.com/Connecting.aspx#