T5 vs. Translated T7 to T5 LSA Forwarding Question

In a normal T5 LSA, the forwarder is set to 0.0.0.0 which means to forward to the originator of the LSA. If the ASBR is not in the local area, use a T4 LSA to locate the ASBR.

In a T5 LSA that has been translated from a T7, the forward address is set to the ASBR in the NSSA that generated the route. When a router tries to locate the forwarder listed in the LSA instead of using a T4 LSA, it uses a T3 LSA.

If the router can use a T3 LSA to locate the ASBR inside of an NSSA, why can it not use a T3 LSA to locate the ASBR in a regular area?

Thanks!