I get the impression from various readmes and from reading the website that J is/was more interested in creating or recreating locations or scenes from films (for example) and in making them as authentic as possible within the confines of the Unreal Engine than he is/was in producing fully playable maps (in the sense of what people expect in a 'normal' DeathMatch map). If you look at the Fringe series of maps, as an example, only one of those is playable as a DM - the accompanying documentation makes it clear that these (and other of his) maps are not intended to be (fully) playable but more something to enter and wander around. Hence the CWO and AeonFlux maps (for example) contain a wide range of references to the films, including bits of the soundtrack and dialogue that would be familar to those who had seen the films, plus character skins, posters, etc.
I don't think there is anything inherently wrong in that approach. Other people have also used the engine for an exercise in recreating architecture and RL spaces - so, for example, there's one map of a university in Portugal which looks like a faithfull reproduction of the campus and, whilst it can be played, there are limitations in the gameplay. All this does, of course, mean one has to adopt a somewhat different set of criteria when viewing and criticising the maps (in essence, one has to look at them differently because the purpose of the map is (in part, largely or wholly) different).