It doesn't make sense to get entangled in that mess unnecessarily. As you say, cryonics is only relevant after legal death. Getting involved before that could indeed be unethical, or at least perceived as such. Outsiders would likely view any discussion of preservation for possible future technological interventions as coercive or manipulative. Actually, I wouldn't be surprised if many cryonicists would object to it as well. After all, many of us are practical enough to realize that the chances of success are small, if not entirely unknown.