We went for a big loop around TN and north GA over the weekend looking for a dealer that could actually sell us an Ariya (they won't) and I test drove 3 different Engage trims which of course all have the smaller 63kwh battery. The first one was indicating 155 miles at 83% SOC, the 2nd was showing 224 miles at 98% and the 3rd was 215 miles at 89%. If you extrapolate these numbers out for 100% SOC (186, 228 and 241) I guess it's possible the Ariya's "GOM" has some bugs to work out.
I guess if you really want to know what's going on maybe try a 55mph range test and see what you get.
The real world energy available is just that so It should be close to 289 miles at those speeds regardless of what the app thinks it is.