On canning, they're backed by over a century of practical information. Canning is essentially the practice of controlling decay. There's not much wiggle room involved when it comes to the pathogenic side of that. The temps at which they die off, or where various toxins are neutralized, have been reproduced so often and so reliably that it's not really in question.

Pork safety comes down to pretty much one pathogen in terms of finished safe temp and time. There's a curve to it. But the USDA (so far) tends to be very sith and deal in absolutes. At 165, with nothing else involved, you know you aren't going to get sick. There's other temps that can get the job done at different times, but we gotta be real about how dumb people are. You start displaying that chart, and the average person will start thinking they can piddle with it.

Plus, going to a lower temp with a rest, or at longer times, you run into more variables in the first place; more room for error to creep in. There's no way I'd recommend that process to someone new to cooking pork, so I can't be upset that the organization that's supposed to be the default source for food safety stays with the most certain path.

Hell, I wouldn't be upset if the USDA only listed canning guidelines that were similarly limited to no brainer numbers. Nuance is for experienced cooks.