I can see some pros and cons with such a system. At first sight it looks advantageous to elites, but is it in the long run?
Let's say there are seats available on a route, and they only show them to elites. But no elite is interested in redeeming. A platinum basic wants to redeem but he cannot because seat is hidden. Seat is left empty on the flight and member still has all his points to burn.
If this happens frequently then lower tier members are accumulating points and has few options to redeem.
Similar case:
Some routes have high revenue demand and only few seats are released. With 1 seat avilable and a staggered access to seats, platinum basic will probably see 0 seats on that flight. So unless you are content on redeeming on DEL you may lose out.
It all depends if they release extra seats for higher tiers or if they just limit the current availability.