The Overnight form doesn’t include it because the Aspen Grove trail doesn’t have any camp locations on it. You have to connect to Fish Creek to get to the nearest camp.
That is the reason, anyway, but I see how it could be a problem searching for a lost person if someone got into trouble between the junction and the trailhead. I will look into updating the form, In the meantime, you can either write it in, or add to the Remarks box to explain you are entering via Aspen Grove. The trail you use has no bearing on whether the permit can be issued, so no worries on that point.