For most MtG players, the game rules are the sum of the game rules and the set of cards which are legal to play. Including other potential card text is not relevant, or at least at that point you are playing an unofficial variant of the game. Also, I think constructing a turing machine just under the comprehensive rules with only ability text is a very simple exercise (even exluding trivial cases like an ability text which simply instructs you to evaluate a turing machine as part of the execution). You could probably print a set of cards to make a usable assembly language, no need for any turing tarpits, which is another reason why no-one is particularly interested in this interpretation of the question.