Originally Posted by
eshroom
Just in case anyonelse stumbles on this post. Yes OSS (through YUL at least) is much quicker than exiting and entering again, but you still get scanned and still lose your over 100mm liquids.
The only reason you had to go through security again was because you were connecting to the US. Americans want people to be searched right before customs up to US TSA standards so they don't try to harm one of their officers and can arrive as a domestic passenger in the US.