Yep. That sounds like what they went through last summer. My understanding - on the other side of the ridge from them, that's exactly what was happening. If you were through hiking, you got sent back to your trailhead to move cars or had to stay on the side where it wasn't burning. The rangers were also evacuating people who got cut off. For my wife and daughter, it meant a lot of ash coming their way and a lot of smoke. Still had a great time though. Beautiful area.
Anyhow, in that terrain, the inReach stuff had a hard time with position reporting. So that might give you some sense for it's performance if you're familiar with the geography of the area.
J.