To these points---
Yes, I explored the abandoned Sassafras trail up beyond that primo CS and even camped on it higher up. It follows an obvious logging cut for several hundred feet and then just disappears---be either crossing the creek or turning into an impassable thicket. Winter would be the best time to follow the creek all the way up to 415.
And yes, that weird cleared Sassy trail above Sassy Falls always gets my curiosity up so on this trip I dumped my pack and followed it over the crossing and the trail starts to peter out but it veers left over a ridge and I think it was an attempt by someone to avoid the nasty Sassafras Creek crossing way below where it crosses Snowbird Creek trail and in high water that crossing ain't easy. Hurricane Laura just ate it's footbridge, btw.
Everybody thinks this above-falls trail climbs to Bee Gap and 415 but as far as I can tell it skirts around a ridge way left of Bee Gap and comes out somewhere on Bird trail below the Sassy crossing.