Has any hacky workaround like this ever held up in a court?
(fixed that for you)
of course they have. For example, having corporate "document retention" policies that are actually destruction policies is usual to avoid risks associated with legal discovery.
And actus reus is a fairly critical technical element of the law. If a company has a policy of issuing (true) warrant canaries, the non-act of not issuing a (false) canary would be a significant technical hurdle to prosecution. And the 1st amendment would be a significant hurdle to coercing a person to issue (false) canaries.