It seems that this can be circumvented by using tabs instead of 4 spaces, given that this answer was successfully posted. I'll admit that I'm not sure exactly where the bug is here.
It could be that the OP, at 161 rep, has graduated above the restriction. In my opinion, no one should be able to add a post which is 100% code. We might relax the ratios based on rep, but 100% code is never appropriate.
It could be that the code detector discovered that the content of the code block is prose. It's still formatted as code, and this shouldn't be allowed.
It could be that the code detector missed that this was going to be formatted as code because it used tabs and not spaces. This seems like the most likely case, given the recent post (that I can't find) about a bug where it allowed an entire post enclosed in backticks.