That would a fascinating comparison to see Eastern bongo in their old exhibit, adjacent to the Lowland nyala in the giraffe exhibit.
I suspect the long term intention is to acquire a bull, which will be housed in the old bongo exhibit; with the cows/calves inhabiting the giraffe exhibit. Aside from bulls being territorial, it’s a good way to manage breeding and similar arrangements have been effective at other zoos in the region.
With Werribee just up the road, I really do not understand the need to accomodate the bull separately. A bull can be kept with the females and any calves in with the giraffes. Contraceptives could be easily used to stop any breeding. Werribee is 45 min away and could accomodate any unwanted calves, especially males.
Keeping the male seperate just seems like a double up of exhibits that doesn't need to happen. Especially when the zoo has its sister zoo just up the road.
Which would lead the zoo to have the space to require bongo and house them. But that would be to logical for current administrators to do.