Once they arrive in Turkey and are housed in UNHCR housing their vetting process begins.  And it is supplemented with Canadian vetting.  Refugees do not hop on a plane of their own choosing and simply come  from Turkey to Canada.  In fact refugees typically do not choose their country of sanctuary.

Lots of people have to flee war zones without documentation; millions of Jews circa 1939 as well.  It doesn't mean their life histories cannot be ascertained.