They receive about 10 applications for each spot, so it is quite competitive It's not actually that "popular" - last year receiving 168 applications - but it has very few places available. As above, it gets a lot of applications from those who think they won't be able to get into the LLB, however the application/acceptance ratios aren't much difference - while the BA is about 50% higher, 50% of a small number is still a small number...
While they may offer some leeway due to there being fewer QLD Law and/with Anthropology courses available in general (I would be honestly somewhat surprised if there were as many as five), but they will probably expect to see some discussion of that aspect of the course. This might be in terms of discussing cultural approaches and interpretations of law and how this relates to for example international law disputes, or working in the legal sector in another country (e.g. empathy with clients, understanding how what judges want to see in a court room - particularly for e.g. civil vs common law). These are all relevant things to discuss for a single honours LLB, but would help demonstrate some awareness of the anthropological aspects.