Maybe it's intentional to actually serve the content but then black it out using a simple script (rather than 503'ing and serving only the blackout page). It's similar to the proposed SOPA censorship in that it only affects the most clueless of us and anyone who really wants to get there can circumvent it.
You can count on one hand the number of people who are both unaware of SOPA and PIPA and know how to disable javascript.