I think I'm beginning to understand this better also.
To add to what was mentioned in that post and drawing (thanks again, Clay), as I slide my thumb along the chamfer (towards the end of the handle), just before reaching the lug, the chamfer has a slight curve that, as the thumb connects with the lug, the thumb changes vector slightly towards the point of the handle directly out from the pivot. That vector change as you connect with the lug begins the opening of the blade. Compared with sliding along the handle, there is some extra resistance at this point as you overcome the detent holding the blade closed. (That resistance seems to reduce over time.) To continue, as your thumb passes the point of the handle out from the pivot, keeping it connected with the lug will have it rotate the blade around the pivot to fully open. (Or, to rephrase this another way, the curve of the chamfer your thumb slides along almost has your thumb scoop the lug away from the handle to open the blade.)
Repeating this pattern is making it a bit easier, though I'm still not sure it will reach the ease of the Inkosi. I'll keep at it (at all of them).