I haven't used a device like this, but I don't think this is exaggeration. It is well known in linguistics that speakers of languages that use absolute directions are better at determining where north is. People that use the chime feature on their watches to indicate every hour also tend to have a better sense of time. It is also a successful tool for people trying to lucid dream (the "reality checks" are similar in behavior). We also know that one can become better at spatial directions through practice, which is why it is "common" advice to drive around when moving to a new city without a GPS (until necessary). It helps build that mental map in your head (which often generalizes) and tells your brain to pay attention to other correlating features (e.g. I wouldn't be surprised if this North Paw experiment gave users better sense of time with respect to the sun).

It should be no surprise that as one becomes accustomed to one's own environment and the way they navigate it.

Though I think the cooler question is if we can build a phone/smart-watch app that can do this. Is there a way to vibrate the watch in a northernly direction or something like vibrating when the user turns north (deceptively tricky).