Politics mostly.

The Gibbs and Cox design was selected because it offered a significantly more capable design than the F100, hence the F100 was deemed inferior to the Gibbs and Cox design.

In particular the F100’s sea keeping was considered a concern given the different wave height and swell length encountered in the Pacific.

Reports from RAN observers on the Spanish F100’s indicated that sea keeping on them was not up to current RAN standards with regard to extent of roll and speed of roll.

The F100 is the fall back if the Gibbs and Cox design falls over, the same as the Leopard 2 was the fall back if the M1 acquisiition fell over.

It didn’t, so it was not needed.

Same goes for the F100, its an insurance policy the RAN has, but desperately does not want to have to use.

Unicorn