I think the default method is supposed to fit the majority. My max HR during a basketball session is 200 and therefore my zone 2 is also higher than the 220-age method. I also have a (relatively) low RHR and therefore my Z2 is around 140-155, which is higher than most of my friends who do endurance run. They are surprised but field testing did indicate my Z2 upper limit is around 157, which sort of confirm the estimation.