Thanks for the lovely write up.
Have to agree the Anoa enclosure seems a bit open. Like Bongo (and to an extent Okapi), I feel that they rarely get enclosures which truly represent the habitats they live in - dense forest with lots and lots of planting. This hasn't seemed to be a major problem for them in zoos, however.
The thing is a lot of species just have to tolerate the more open enclosures they find themselves in in zoos. At Whipsnade I've found the Bongo are usually using either the small wooded area along the perimeter fence of their enclosure or, perhaps more usually, in the inside stables. At Howletts/PL I have rarely seen the Bongo over many years, they seem invisible and I suspect are resting directly behind the shed/shelter where they are out of view of visitors. So 'secretive' species like this may actually benefit far more (and perhaps show themselves better) from more extra cover than is usually available.