An additional (afterthought), the wrinkle rule works with high quality, high TPI, high $$$ tires ... not as helpful with more affordable, lower TPI tires.
Winter pressures are truly more complex when you ride more than single-track trails and similar conditions. I ride my fat bike on the roads with bare pavement, on plowed rail-trails with snow pack and ice, on icy lakes with drifts, in addition to snowy single-track trails.