you have to go in without too many expectations because it all depends on how many people with shared dna have had the test done...so that confounds for education, culture, finances etc. also, if you have lived in Greece for 20 generations, you probably don't have burning curiousity about who your ancestors are...so perhaps not a whole lot of greeks have taken the test...or if your ancestors stayed in a greek community in Canada and did not intermarry etc...

there are also adoptions, rapes, etc...not everything follows the family tree.

but I just heard from someone else with a geographic similarity...probably some dingle connection although I am not aware of the surname on the family tree...on the other hand I can only go back three generations on my father's side, and that is for three ggfathers and one and perhaps two ggmothers...one ggmother..absolutely nothing is known but she is the only one we knew any story at all about..although it turns out it was wrong.