On the european airlines I fly, you can still select the preferred seat type in advance, just not the actual row you're in. If this is prioritised correctly (by booking time, or perhaps just price - I don't know), then where is the issue in not allowing advance seat selection?

Note: you can still select those seats in advance if you have status or a high enough fare, this only affects non-status passengers, I fail to see how this is discriminatory in any way, especially considering the groups are still assigned towards the back.