NV OSTrlMoa ends at a truck rest area on I-15, but that point doesn't correspond to anything on I-15, so the last segment isn't automatically recognized as traveled just because I-15 has been.
Also, the trail sign in the rest area says it's for the next 16 miles southbound, but TM has it going to the the exit after that, 20 miles away. Perhaps in the northbound direction, it should be shown as going to the Carp Elgin Rd exit, which is another 4-5 miles away. It's not like you can get off at the rest area and go somewhere else, or even turn around.
https://maps.app.goo.gl/f7fj5DruoBjEuzyw7