It's most likely the magazine that the FNH High Power uses that's banned.
NSW has restrictions on the ways that a larger capacity magazine can be restricted to 10 rounds if they consider it too easy to revert it back to original capacity.
It's not a Browning, it is Fabrique National's new remake of the GP35 and listed under FN handguns. The barrel is 120mm, but the original mag is 17 rounds and probably pinned to 10, so rc42 would be on the money about how NSW determine mag capacity restricting.