I can see the FDA hiring people to spot check stores to make sure the nutrition labels face out.
If it’s not in the law, how can they? No law saying they can’t stock boxes in any orientation they like. OTOH, you’re probably right in the sense that it’s a pretty foreseeable scenario, and they often do anticipate those in new legislation.
OR...they’ll just mandate the information be on BOTH sides. Then we’re screwed and it’s impossible to make our own decisions about how to stock.