You can't game your way around that.. the court will care about outcome, not method.
Now that, that is genius.
If the intent was to communicate, I don't see how the fact that it's a side channel is relevant.
To me, the notion that the second shouldn't be possible is common sense. I find it hard to express how little it surprises me that you do not share this perspective.
Not that I agree with gag orders attached to warrants, mind you. But saying that it's just "stopping a process running on my computer" not "communicating information" is just wrong from an information theoretic point of view. Lots of things can be used as a semaphore to communicate information. I bet in other contexts (say insider trading), you'd agree that it doesn't matter whether some CEO tipped off his buddy about insider information by carefully varying load on a server to modulate response times on a web page, thus communicating bits of information.
Ah, but what if the CEO is just taking a long time to reply to emails from friends, because he is very busy preparing for some huge business move -- is it insider trading if one of those friends sets up an options position that profits from increased volatility? This gets down to the difference between a side channel (inadvertent) and a covert channel (deliberate). The distinction does not matter from an information theoretic point of view; the same information is communicated in either case.
I do not doubt that they have constructed for themselves a legal scenario that allows them to command warrant canary operators to lie. On the contrary, I am suggesting that they have with all likelyhood done exactly that.
The situation is constructed by the canary operator; the legal situation, the justification for commanding the canary operator to lie, is not constructed by the canary operator. As much as they would like to be, the canary operator is not in a position to dictate how the laws are written and interpreted.
If the canary operator were in a position to construct the legal situation, then there would be no cause for concern. However they are not, and cannot be.