I think this is a more general policy across the Stack Overflow family of sites (even if it's not official on any except Super User). I had a community wiki question closed on Stack Overflow, because it dealt specifically with a website UI and asked for examples that web developers ought to learn from (in the vein of the book Beautiful Code). Yet the same question specifically for application UI is perfectly acceptable. (And probably necessary, since the general thread on this has a lot of websites.)
Right now web applications are in that "awkward phase" - they're not accepted as "real programs" by a lot of smart people, programmers and non-programmers alike. Most people now in the field are probably too young to remember it, but personal computers went through the same phase. ("Real programs" ran on mainframes and, later, minicomputers - someone who specialized in microcomputer programming was... well, no one was sure what, but certainly not a programmer.) I don't think the policy will change until this does.
